What is lightning?

Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground. In the early stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground. When the opposite charges build up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning. The flash of lightning temporarily equalizes the charged regions in the atmosphere until the opposite charges build up again.

Lightning can occur between opposite charges within the thunderstorm cloud (intra-cloud lightning) or between opposite charges in the cloud and on the ground (cloud-to-ground lightning).

Lightning is one of the oldest observed natural phenomena on earth. It can be seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, in large hurricanes, and obviously, thunderstorms.

What causes thunder?

Lightning causes thunder! Energy from a lightning channel heats the air briefly to around 50,000 degrees Fahrenheit, much hotter than the surface of the sun. This causes the air to explode outward. The huge pressure in the initial outward shock wave decreases rapidly with increasing distance and within ten yards or so has become small enough to be perceived as the sound we call thunder.

Thunder can be heard up to 25 miles away from the lightning discharge, but the frequency of the sound changes with distance from the lightning channels that produce it, because higher frequencies are more quickly absorbed by the air. Very close to lightning, the first thunder you hear is from the closest channels,which produce a tearing sound, because that thunder contains high frequencies. A few seconds later, you hear a sharp click or loud crack from lightning channels a little farther away, and several tens of seconds later the thunder from the most distant part of a flash has quieted to low frequency rumbling.

Because light travels through the air roughly a million times faster than sound does, you can use thunder to estimate the distance to lightning. Just count the number of seconds from the time you see a flash until you hear thunder. Sound travels approximately one fifth of a mile per second or one third of a kilometer per second, so dividing the number of seconds by 5 gives the number of miles to the flash and dividing by 3 gives the number of kilometers.

Where does lightning strike?

Most, if not all, lightning flashes produced by storms start inside the cloud. If a lightning flash is going to strike ground, a channel develops downward toward the surface. When it gets less than roughly a hundred yards of the ground, objects like trees and bushes and buildings start sending up sparks to meet it. When one of the sparks connects the downward developing channel, a huge electric current surges rapidly down the channel to the object that produced the spark. Tall objects such as trees and skyscrapers are more likely than the surrounding ground to produce one of the connecting sparks and so are more likely to be struck by lightning. Mountains also make good targets. However, this does not always mean tall objects will be struck. Lightning can strike the ground in an open field even if the tree line is close by.

What causes lightning?

The creation of lightning is a complicated process. We generally know what conditions are needed to produce lightning, but there is still debate about exactly how a cloud builds up electrical charges, and how lightning forms. Scientists think that the initial process for creating charge regions in thunderstorms involves small hail particles called graupel that are roughly one quarter millimeter to a few millimeters in diameter and are growing by collecting even smaller supercooled liquid droplets. When these graupel particles collide and bounce off of smaller ice particles, the graupel gains one sign of charge and the smaller ice particle gains the other sign of charge. Because the smaller ice particles rise faster in updrafts than the graupel particles, the charge on ice particles separates from the charge on graupel particles, and the charge on ice particles collects above the charge on graupel.

Laboratory studies suggest that graupel gains positive charge at temperatures a little colder than 32 degrees Fahrenheit, but gains negative charge at colder temperatures a little higher in the storm. Scientists think the two largest charge regions in most storms are caused mainly by graupel carrying negative charge in the miple of the storm and ice particles carrying gained positive charge in the upper part of the storm. However, a small positive charge region often is below the main negative charge region from graupel gaining positive charge at lower, warmer altitudes. Small ice particles that have collided with negative graupel in the lower region can contribute positive charge to the miple of the storm.

A conceptual model shows the electrical charge distribution inside deep convection (thunderstorms), developed by NSSL and university scientists. In the main updraft (in and above the red arrow), there are four main charge regions. In the convective region but outside the outdraft (in and above the blue arrow), there are more than four charge regions.
 

How is electrical charge distributed through a thunderstorm?

A conceptual model shows the electrical charge distribution inside deep convection (thunderstorms), developed by NSSL and university scientists. In the main updraft (in and above the red arrow), there are four main charge regions. In the convective region but outside the outdraft (in and above the blue arrow), there are more than four charge regions.

Lightning can strike anyplace on Earth. In fact, there are about 6,000 lightning strikes every minute, which is more than 8 million strikes every day. You can protect yourself and your loved ones if you know what to do when you see lightning or when you hear thunder as a warning. The risk of being struck by lightning is low, but the consequences of lightning strike injuries are serious. From 2006 through 2021, lightning caused an average of 28 deaths per year in the United States.

Lightning is fascinating to watch but also extremely dangerous. In the United States, there are about 25 million lightning flashes every year. Each of those 25 million flashes is a potential killer. While lightning fatalities have decreased over the past 30 years, lightning continues to be one of the top weather killers in the United States. In addition, lightning injures many more people than it kills and leaves some victims with life-long health problems.

Understanding the dangers of lightning is important so that you can get to a safe place when thunderstorms threaten. If you hear thunder—even a distant rumble—you are already in danger of becoming a lightning victim.

How Thunderstorms Develop

All thunderstorms go through stages of growth, development, electrification and dissipation. Thunderstorms often begin to develop early in the day when the sun heats the air near the ground and pockets of warmer air start to rise in the atmosphere. When these pockets of air reach a certain level in the atmosphere, cumulus clouds start to form. Continued heating causes these clouds to grow vertically into the atmosphere. These "towering cumulus" clouds may be one of the first signs of a developing thunderstorm. The final stage of development occurs as the top of the cloud becomes anvil-shaped.

As a thunderstorm cloud grows, precipitation forms within the cloud. A well-developed thunderstorm cloud contains mostly small ice crystals in the upper levels of the cloud, a mixture of small ice crystals and small hail in the middle levels of the cloud, and a mixture of rain and melting hail in the lower levels of the cloud. Air movements and collisions between the various types of precipitation in the middle of the cloud cause the precipitation particles to become charged. The lighter ice crystals become positively charged and are carried upward into the upper part of the storm by rising air.

The heavier hail becomes negatively charged and is either suspended by the rising air or falls toward the lower part of the storm. These collisions and air movements cause the top of the thunderstorm cloud to become positively charged and the middle and lower part of the storm to become negatively charged.

In addition, a small positive charge develops near the bottom of the thunderstorm cloud. The negative charge in the middle of thunderstorm cloud causes the ground underneath to become positively charged, and the positively charged anvil causes the ground under the anvil to become negatively charged.

How Lightning Forms

Lightning is a giant spark of electricity in the atmosphere or between the atmosphere and the ground. In the initial stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground; however, when the differences in charges becomes too great, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning.

Lightning can occur between opposite charges within the thunderstorm cloud (Intra Cloud Lightning) or between opposite charges in the cloud and on the ground (Cloud-To-Ground Lightning). Cloud-to-ground lightning is divided into two different types of flashes depending on the charge in the cloud where the lightning originates.

Thunder

Thunder is the sound made by a flash of lightning. As lightning passes through the air it heats the air quickly. This causes the air to expand rapidly and creates the sound wave we hear as thunder. Normally, you can hear thunder about 10 miles from a lightning strike. Since lightning can strike outward 10 miles from a thunderstorm, if you hear thunder, you are likely within striking distance from the storm.

About 40 million lightning strikes hit the ground in the United States each year. But the odds of being struck by lightning in a given year are less than one in a million, and almost 90% of all lightning strike victims survive. The odds of being struck multiple times is even less, with the record being seven times in one lifetime. There are some factors that can put you at greater risk for being struck, such as participating in outdoor recreational activities or working outside. Regional and seasonal differences can also affect your risk of being struck by lightning.

Lightning Strike Injuries and Deaths Vary by Region

Although lightning affects all regions in the United States, the Southeastern states are most at risk. Lightning generally decreases from the southeast to the northwest, except for a few places, such as the Rocky Mountains, where thunderstorms occur regularly during the summer.

Florida, Texas, Colorado, North Carolina, Alabama, Arizona, Georgia, Missouri, New Jersey, and Pennsylvania have the most lightning deaths and injuries. Florida is considered the “lightning capital” of the country, with more than 2,000 lightning injuries over the past 50 years.

Since 2006, only five states (Alaska, Delaware, Hawaii, New Hampshire, Washington) and the U.S. Virgin Islands have reported no lightning deaths.

Quick Facts

• From 2006 through 2021, there were 444 lightning strike deaths in the United States.
• Males are four times more likely than females to be struck by lightning.
• The average age of a person struck by lightning is 37 years.
• About one-third of lightning injuries occur indoors.

Lightning Deaths are Most Common in the Summer

Lightning can occur during any time of the year, but most lightning deaths occur during summer, especially during July.

Did You Know?

Lightning deaths often occur on weekends, particularly Saturdays, and in the afternoon. In fact, two out of three lightning deaths occur between noon and 6 p.m.

Participating in Certain Activities Increases the Risk of Being Struck by Lightning

Lightning most often strikes people who engage in outdoor recreational activities or work outside. From 2006 through 2021, leisure activities such as fishing, boating, playing sports, and relaxing at the beach accounted for almost two-thirds of lightning deaths.

Work-related activities contribute to about 18% of total lightning fatalities, with farmers and ranchers at highest risk. Most work-related lightning strikes are among males.

Most lightning starts inside a thunderstorm and travels through the cloud. It can then stay within the cloud or continue to travel through the open air and eventually to ground. There are roughly 5 to 10 times as many flashes that remain in the cloud as there are flashes which travel to the ground, but individual storms may have more or fewer flashes reaching ground. Lightning can strike where it’s not raining, or even before rain reaches the ground!

Cloud-to-Ground Flashes

Does lightning go up or down? There are two ways that flashes can strike ground: naturally downward (those that occur because of normal electrification in the environment), and artificially initiated or triggered upward. Artificially initiated lightning is associated with things like very tall structures, rockets and towers. Triggered lightning starts at the “ground,” which in this case may mean the top of a tower, and travels upward into the cloud, while “natural” lightning starts in the cloud and travels to ground. Upward triggered lightning usually occurs in response to a natural lightning flash, but on rare occasions can be “self-triggered”—usually in winter storms with strong winds. Lightning can also be triggered by aircraft flying through strong electric fields. If the plane is below the cloud, then a CG flash could result.

In the most common type of cloud-to-ground lightning (CG), a channel of negative charge, called a stepped leader, will zigzag downward in roughly 50-yard segments in a forked pattern. This stepped leader is invisible to the human eye, and shoots to the ground in less time than it takes to blink. As it nears the ground, the negatively charged stepped leader causes streamer channels of positive charge to reach upward, normally from taller objects in the area, such as a tree, house, or telephone pole. When the oppositely-charged leader and streamer connect, a powerful electrical current begins flowing. This return stroke current of bright luminosity travels about 60,000 miles per second back towards the cloud. A negative CG flash consists of one or perhaps as many as 20 return strokes. We see lightning flicker when the process rapidly repeats itself several times along the same path. The actual diameter of the lightning channel current is one to two inches, surrounded by a region of charged particles.

The more common cloud-to-ground flash has a negative stepped leader that travels downward through the cloud, followed by an upward traveling return stroke. The net effect of this flash is to lower negative charge from the cloud to the ground so it is commonly referred to as a negative CG (or -CG). Less commonly, a downward traveling positive leader followed by an upward return stroke will lower positive charge to earth, referred to as a positive CG (or +CG). +CG flashes typically have only a single return stroke, and they are more likely than -CGs to have a sustained current flow. Some storms produce more positive than negative CGs because of the charge distribution in the storms, but+CG dominated storms are not as common. Storms which produce mostly negative CGs tend to produce CGs earlier in the storm lifecycle and produce significantly more CGs than similar storms which instead produce mostly positive CGs.

A “bolt from the blue” is a CG which starts inside a cloud, goes out the side of the storm, then travels horizontally away from the cloud before going to ground. A bolt from the blue can strike ground at a spot with “blue sky” above it. So even a storm that is 6 miles away can be dangerous.

Cloud Flashes

There are many flashes which do not reach ground. Most of these remain within the cloud and are called intra-cloud (IC) lightning flashes. Cloud flashes sometimes have visible channels that extend out into the air around the storm (cloud-to-air or CA), but do not strike the ground. The term sheet lightning is used to describe an IC flash embedded within a cloud that lights up as a sheet of luminosity during the flash.

Other Lightning-Related Terms

A related term, heat lightning, is any lightning (IC or CG) or lightning-induced illumination that is too far away for the thunder to be heard. It may have reddish (“heat”) color, like sunsets, because of scattering of blue light. There are a lot of misconceptions about heat lightning, but it’s no different than regular lightning. Lightning can also travel from one cloud to another, or cloud-to-cloud (CC). Spider lightning refers to long, horizontally traveling flashes often seen on the underside of stratiform clouds. Spider lightning is often linked to +CG flashes.

Transient Luminous Events

Large thunderstorms are capable of producing other kinds of electrical phenomena called transient luminous events (TLEs) that occur high in the atmosphere. They are rarely observed visually and not well understood. The most common TLEs include red sprites, blue jets, and elves.

Sprites can appear directly above an active thunderstorm as a large but weak discharge. They usually happen at the same time as powerful positive CG lightning strokes. They can extend up to 60 miles from the cloud top. Sprites are mostly red and usually last no more than a few seconds, and their shapes are described as resembling jellyfish, carrots, or columns. Because sprites are not very bright, they can only be seen at night. They are rarely seen with the human eye, so they are most often imaged with highly sensitive cameras.

Fun fact: Aircraft pilots occasionally reported seeing lightning above storms for many years before researchers documented sprites and other TLEs with sensitive video cameras.

Blue jets and gigantic jets emerge from the top of the thundercloud, but are not directly associated with cloud-to-ground lightning. They extend up in narrow cones fanning out and disappearing at heights of 25-35 miles. Gigantic jets go even higher to the ionosphere. Blue jets last a fraction of a second and have been witnessed by pilots.

Elves are rapidly expanding disk-shaped regions of glowing that can be up to 300 miles across. They last less than a thousandth of a second, and occur above areas of active cloud to ground lightning. Elves result when an energetic electromagnetic pulse extends up into the ionosphere. Elves were discovered in 1992 by a low-light video camera on the Space Shuttle, and are now known to be associated with terrestrial gamma ray flashes (TGFs). TGFs were discovered in the 2000s by satellites designed to detect cosmic gamma rays, but it was found that some signals were coming from thunderstorms on earth! TGF appear to originate where strong electric fields exist in a deep region to act as a particle accelerator that is seeded by cosmic ray particles. This can also produce beams of relativistic electrons. Normal lightning also produces x-rays that can be detected at the ground.

Lightning Detection Networks

Currently, cloud-to-ground (CG) and intra-cloud (IC) lightning flashes are detected and mapped in real-time by two different networks in the United States--the National Lightning Detection Network (NLDN), a system owned and operated by Vaisala Inc, and the Earth Networks Total Lightning Network. These two systems work by detecting radio waves (sferics) emitted by fast electric currents (strokes) in lightning channels. A “stroke” can be a fast current within the cloud, or a “return stroke” in a channel to ground. CG return strokes usually have larger currents that make stronger signals that are easier to detect. Since there are many other sources of radio noise, the systems have to first identify which bursts are likely to be caused by lightning. Radio signals are detected by multiple stations (at least 3) are used to determine the location of the stroke by a time-of-arrival technique. Location accuracy is best when lightning occurs within a network of stations. Flashes outside of the network have larger location errors and may not even be detected.

Each system may detect more than one stroke (in-cloud or return) for a single lightning flash. CG flashes that bring negative charge from the cloud to ground (“negative CG” or “-CG”) can have multiple return strokes, which can sometimes be seen visually as a flickering of the channel to ground. Positive CG (+CG) flashes effectively bring positive charge to ground (or negative charge up) and almost always have only a single return stroke. The +CG return stroke, however, more often has a sustained current that can have greater chance of igniting fires.

What we do: NSSL uses the data collected by the NLDN to learn how storms produce CG flashes and how these flashes relate to other storm hazards.

Lightning Mapping Arrays

Lightning Mapping Arrays provide three-dimensional mapping of lightning channel segments near the array. Up to thousands of points can be mapped for an individual lightning flash to reveal its location and the development of its structure. Research LMA's exist in Oklahoma, the Texas Panhandle, northern Alabama, Washington D.C., Kennedy Space Center in Florida, and many other locations. NSSL is currently building a mobile array in order to provide targeted lightning observations in conjunction with field campaigns.

LMA systems also detect radio noise, but in the very high frequency (VHF) band around 60 MHz. They also use a time-of-arrival technique to locate source points in 3 dimensions and time, usually using at least 6 or 7 stations to keep errors lower. High time resolution (20 to 100 ns) makes it possible to watch lightning progress from initiation into different regions of storms. Sometimes flashes are very small and last only a few milliseconds, but some can cover very large areas and keep going for up to 6-7 seconds.

What we do: NSSL uses the OKLMA to investigate how lightning characteristics relate to updrafts, precipitation, and severe storm processes. Scientists also use the OKLMA to investigate using lightning data in weather forecast models.

Geostationary Lightning Mapper

The Geostationary Lightning Mapper (GLM) is an instrument on two weather satellites launched in 2016 and 2018 (GOES-16 and GOES-17) that map total lightning (in-cloud and cloud-to-ground) activity continuously day and night over the Americas and adjacent ocean regions. The GLM monitors the optical emissions of lightning which reach space, similar to what we would see with our eyes. It records how bright the flashes are from above, how large of an area a flash covers, and how many flashes pass over any given location. It cannot, however, “see” if a channel from the flash hits ground or not.

The GLM is essentially a fast infrared video camera. It “sees” in a particular narrow band of light that lightning emits well and helps distinguish from other sources of light. It can record about 500 images per second, which is fast enough to see the progression of lightning as it brightens different parts of a cloud. The spatial resolution is about 8 km, which is about the size of a small thunderstorm, so each camera pixel can see about one whole small storm or part of a large storm. Some very large storm systems like squall lines have been seen to make lightning flashes that traverse 100s of kilometers across the storm!

GLM lightning data provide many new applications for total lightning that were not possible over large areas of the country previously. It can be used by aviation weather services to monitor the spatial coverage of lightning. It will be useful for climatological studies of total lighting and thunderstorm activity. It provides new information on the lightning in hurricanes before they make landfall. It provides information over a large area on storm conditions which may improve weather models and is currently being tested by NSSL scientists. The GLM also helps to identify growing, active, and potentially destructive thunderstorms over the entire country (as well as ocean areas) which can help forecasters monitor thunderstorms and issue severe thunderstorm warnings.

What we do: NSSL and partners are working on applications and products that use the GLM. Scientists also use trends in the flash rates to help identify the development of thunderstorms, the growth of updrafts, and the formation of precipitation and downdrafts.

Other Lightning Sensors

Flashes have also been detected from space during the past few decades by other optical sensors which preceded the GLM - the Optical Transient Detector and the Lightning Imaging Sensor. The Optical Transient Detection was the experimental instrument launched in 1995 before the Lightning Imaging Sensor. The Lightning Imaging Sensor on the TRMM satellite covered the earth twice a day in tropical regions from 1998 to 2014. Most recently, the spare Lightning Imaging Sensor was mounted on the International Space Station in 2017. The Lightning Imaging Sensor has better resolution than the GLM, but only briefly scans small areas as it passes overhead.

Each of the sensors above measures a different part of the process of a lightning flash. The neworks which detect CGs respond to the high currents and large transfers of charge during a flash. The LMA responds to the VHF radiation emitted as a lightning channel develops. The optical measurements from space respond to the optical emissions from lightning which escape the top of the cloud. This means that each one tells you something different about the lightning in a storm! It also means that the definition of a “lightning flash” can depend on (or is limited by) how it is observed.

Forecasters can and do forecast the likelihood of intense lightning activity. However, it is impossible to forecast individual strikes because lightning is so widespread, frequent and random. Our understanding of cloud electrification processes is still incomplete, but we do know some of the ingredients that a storm needs in order to become electrified and potentially produce lightning. There are two big methods used to look at these ingredients: (1) observation of the current weather, and (2) computer forecast models of the future weather.

Observations of Current Weather

Scientists use characteristics of the current weather in order to forecast if and where a storm is likely to produce lightning in the future. The current weather is very important to forecasting lightning in the next hour. In order to do this well, there are many things that we need to know about the storm. Has it produced lightning before? Is it currently growing in size? Does the storm reach altitudes where temperatures are below freezing? How is the storm moving? How old is the storm? We can compare this type of information to cases that have happened before and then predict the probability of if and the general area where a storm might produce lightning. Scientists make a probabilistic prediction of lightning because weather is a chaotic system, so one small change in the storm or the surrounding environment can make a big difference.

Computer Forecast Models

To determine whether or not a storm is likely to produce lightning over an hour from now, scientists need to use a computer forecast model. Unfortunately, it is still very computationally expensive to directly simulate how lighting behaves, like where it starts and how it branches. NSSL scientists do use this type of simulation in research, but use other things for forecasting lightning. Similar features that are useful in predicting lightning from the current weather can be used in an existing weather forecast model. If a storm exists in a weather forecast model, how large is it? Does it contain both ice particles and water droplets? How much ice does it contain that might be carrying charge? Is there a lot of air moving rapidly upwards within the storm? With this sort of information we can use statistical relationships to predict the probability of lightning well in the future!

What is my risk of being struck by lightning?

The odds of being struck by lightning in a given year is less than one in a million. You might have a higher risk if you work outside or live in certain parts of the country, such as Florida or Texas.

Who is at greatest risk for lightning strikes?

Males are four times more likely than females to be struck by lightning. Most lightning strike victims are people who regularly participate in outdoor recreation activities or work outside. Construction and farming are the two most common occupations for victims of lightning strikes. Regional and seasonal differences and time of day and year affect the risk of lightning injury. For instance, most lightning strikes occur in the summer months, especially July, during the afternoon and evening. Also, southeastern states are particularly at risk, with Florida and Texas having the largest number of lightning-related deaths.

Is it safe to touch somebody who was struck by lightning?

Yes. Lightning victims DO NOT carry an electrical charge and you will NOT be electrocuted by touching someone who has been struck. It is safe to touch a lightning victim and administer first aid immediately. For more information, visit the Lightning First Aid Recommendations webpage.

What should I do if I see someone get struck by lightning?

Immediately call 911 for help. It is safe to touch a lightning victim and administer first aid immediately. For more information, visit the Lightning First Aid Recommendations webpage.

How many people are injured from lightning strikes each year in the United States?

Lightning strike injuries are not well documented. However, it is estimated that about 180 people are injured each year due to lightning.

How many people die from lightning strikes each year in the United States?

About 10% of people struck by lightning die. From 2006 through 2021, lightning caused an average of 28 deaths per year.

What happens to the body as a result of a lightning strike?

About 10% of people struck by lightning die, most commonly because of a heart attack. Other lightning injuries include blunt trauma, neurological syndromes that are usually temporary, muscle injuries, eye injuries (“lightning-induced cataract”), skin lesions, and burns.

How does lightning cause injuries?

Lightning can cause injuries in several ways:

• Direct strike: A direct strike is often fatal.
• Contact injury: Lightning strikes an object, such as a car or metal pole, that the victim is touching.
• Side flash: Lightning splashes or bounces off an object, such as a tree or person, onto the victim.
• Ground current: Lightning strikes the ground near a victim and the ground current passes from the strike point through the ground and into the victim.
• Streamer: When the air is charged with electricity during a lightning storm, bursts of energy, or streamers, can come upward from objects near the ground. Sometimes these streamers travel upwards through people, causing harm.
• Blast injury: The lightning’s blast effect and sound might directly cause injury, such as ruptured eardrums, or might cause the person to fall or be thrown against an object.

Giving first aid to a person who has been struck by lightning while waiting for professional medical attention can save their life. It is safe to touch people who have been struck by lightning; they DO NOT carry an electrical charge.

How to Help

Follow these four steps immediately to help save the life of a person who has been struck by lightning:

1. CALL FOR HELP

   Call 911 immediately. Give directions to your location and information about the person. It is safe to use a cell phone or cordless phone during a storm.

   Items to Note When Calling for Help

   • How many people were struck?
   • Where were they struck?
   • Is the storm continuing?
2. ASSESS THE SITUATION
   Safety is a priority. Be aware of the continued lightning danger to both the person who has been struck and the rescuer. If located in a high-risk area (for example, near an isolated tree or in an open field), you could be in danger. If necessary, move to a safer location.

   It is unusual for a person who has survived a lightning strike to have any major broken bones that would cause paralysis or major bleeding complications, unless the person suffered a fall or was thrown a long distance. Therefore, it might be safe to move the victim to reduce the risk of further exposure to lightning. Do not move victims who are bleeding or appear to have broken bones.

   People who have been struck by lightning do not carry an electrical charge and can be handled safely.

3. RESPOND

   Lightning often causes a heart attack. Check to see if the person is breathing and has a heartbeat. The best places to check for a pulse are the carotid artery in the neck and the femoral artery in the groin.

   If the person is breathing normally, look for other possible injuries. Lightning can cause burns, shock, and sometimes blunt trauma. Treat each of these injuries with basic first aid until help arrives. If the area is cold and wet, putting a protective layer, such as a jacket, blanket, or plastic sheet, between the person and the ground may help decrease hypothermia (abnormally low body temperature).

4. RESUSCITATE

   If the person is not breathing, immediately begin mouth-to-mouth rescue breaths. If they do not have a pulse, start chest compressions as well (CPR). Continue resuscitation efforts until help arrives.

Learn how to protect yourself and your loved ones during a thunderstorm. Being outside when lightning is present is not something to take lightly—ever.

The weather forecast calls for a slight chance of thunderstorms, but you can only see a few fluffy white clouds overhead. So, you and your tennis partner grab your racquets and balls and head for the tennis court. You spend a few minutes warming up and then—wait! Is that thunder you hear? Was that a lightning flash?

What do you do? Keep playing until the thunder and lightning get closer? Go sit on the metal bench under the trees to see what happens? Or get in your car and drive home?

Correct answer: If no substantial, non-concrete shelter is nearby, get in your car and wait out the storm.

Why? Because being outside when lightning is present is not something to take lightly—ever.

Risks of Lightning Strikes

Although the odds of being struck by lightning each year are less than 1 in a million, some factors can put you at greater risk. Lightning most often strikes people who work outside or engage in outdoor recreational activities. Regional and seasonal differences can also affect your risk of being injured by lightning.

In 2021, Florida had the most lightning deaths. Florida is considered the “lightning capital” of the country, with more than 2,000 lightning injuries over the past 50 years.

The consequences of lightning strikes are serious. From 2006 through 2021, lightning caused an average of 28 deaths per year in the United States.

Protect Yourself from Lightning Strikes

Safety precautions outdoors

You can protect yourself from risk even if you are caught outdoors when lightning is close by.

• If the weather forecast calls for thunderstorms, postpone your trip or activity.
• Remember: When thunder roars, go indoors. Find a safe, enclosed shelter. Safe shelters include homes, offices, shopping centers, and hard-top vehicles with the windows rolled up.
• If you are caught in an open area, act quickly to find adequate shelter. The most important action is to remove yourself from danger. Crouching or getting low to the ground can reduce your chances of being struck but does not remove you from danger. If you are caught outside with no safe shelter nearby, the following actions may reduce your risk:
  • Immediately get off elevated areas such as hills, mountain ridges, or peaks.
  • Never lie flat on the ground. Crouch down in a ball-like position with your head tucked and hands over your ears so that you are down low with minimal contact with the ground.
  • Never shelter under an isolated tree.
  • Never use a cliff or rocky overhang for shelter.
  • Immediately get out of and away from ponds, lakes, and other bodies of water.
  • Stay away from objects that conduct electricity (such as barbed wire fences, power lines, or windmills).
• If you are in a group during a thunderstorm, separate from each other. This will reduce the number of injuries if lightning strikes the ground.
• If you are out in the open water and a storm rolls in, return to shore immediately.
• Avoid open vehicles such as convertibles, motorcycles, and golf carts.
• Avoid open structures such as porches, gazebos, baseball dugouts, and sports arenas. These structures won’t protect you from lightning.
• Stay away from open spaces such as golf courses, parks, playgrounds, ponds, lakes, swimming pools, and beaches. Seek shelter immediately.
• Stay away from tall structures, such as telephone poles and trees; lightning tends to strike the tallest object around.

Safety precautions indoors

Being indoors does not automatically protect you from lightning. In fact, about one-third of lightning-strike injuries occur indoors. Here are some tips to keep safe and reduce your risk of being struck by lightning while indoors.

• Avoid contact with water during a thunderstorm. Do NOT bathe, shower, wash dishes, or have any other contact with water during a thunderstorm. Lightning can travel through plumbing.
• Avoid using electronic equipment of all types. Do NOT use anything connected to an electrical outlet, such as computers, laptops, game systems, washers, dryers, or stoves. Lightning can travel through electrical systems and radio and television reception systems.
• Avoid using corded phones. Corded phones are NOT safe to use during a thunderstorm. However, cordless or cellular phones are safe to use during a storm.
• Do NOT lie on concrete floors or lean on concrete walls during a thunderstorm. Lightning can travel through any metal wires or bars in concrete walls or flooring.

Lightning strikes may be rare, but they still happen, and the risk of serious injury or death is severe. Take thunderstorms seriously. Learn and follow the above safety rules to keep yourself safe from lightning.

Indoor Safety Tips

Even though your home is a safe shelter during a lightning storm, you might still be at risk. About one-third of lightning-strike injuries occur indoors. Here are some tips to keep safe and reduce your risk of being struck by lightning while indoors.

• Avoid water.
  Do NOT bathe, shower, wash dishes, or have any other contact with water during a thunderstorm because lightning can travel through a building’s plumbing. The risk of lightning travelling through plumbing might be less with plastic pipes than with metal pipes. However, it is best to avoid any contact with plumbing and running water during a lightning storm to reduce your risk of being struck.
• Don’t touch electronic equipment.
  Do NOT use anything connected to an electrical outlet, such as computers, laptops, game systems, washers, dryers, or stoves. Lightning can travel through electrical systems, radio and television reception systems, and any metal wires or bars in concrete walls or flooring. Equip your home with whole-house surge protectors to protect your appliances.
• Avoid windows, doors, porches, and concrete.
  Stay away from windows and doors, and stay off porches. Do NOT lie on concrete floors or lean on concrete walls during a thunderstorm. Lightning can travel through any metal wires or bars in concrete walls or flooring.
• Don’t use corded phones.
  Corded phones are NOT safe to use during a thunderstorm. Do NOT use them. However, it is safe to use cordless or cellular phones during a storm.

Outdoor Safety Tips

Although no place outside is safe during a thunderstorm, you can minimize your risk by assessing the lightning threat early and taking appropriate actions. The best defense is to avoid lightning. Here are some outdoor safety tips that can help you avoid being struck.

• Be aware.
  Check the weather forecast before participating in outdoor activities. If the forecast calls for thunderstorms, postpone your trip or activity, or make sure suitable safe shelter is readily available.
• Go indoors.
  Remember the phrase, “When thunder roars, go indoors.” Find a safe, enclosed shelter when you hear thunder. Safe shelters include homes, offices, shopping centers, and hard-top vehicles with the windows rolled up.
• Seek shelter immediately, even if caught out in the open.
  If you are caught in an open area, act quickly to find shelter. The most important action is to remove yourself from danger. Crouching or getting low to the ground can reduce your chances of being struck, but it does not remove you from danger.
• If you are caught outside with no safe shelter nearby, the following actions might reduce your risk of being struck by lightning:
  • Immediately get off elevated areas such as hills, mountain ridges, or peaks.
  • Never lie flat on the ground. Crouch down in a ball-like position with your head tucked and hands over your ears so that you are down low with minimal contact with the ground.
  • Never shelter under an isolated tree. If you are in a forest, shelter near lower trees.
  • Never use a cliff or rocky overhang for shelter.
  • Immediately get out of and away from ponds, lakes, and other bodies of water.
  • Stay away from objects that conduct electricity (such as barbed wire fences, power lines, or windmills).

• Separate from others.
  If you are in a group during a thunderstorm, separate from each other. This will reduce the number of injuries if lightning strikes the ground.

• If you are out in the open water and a storm rolls in, return to shore immediately.
  If you are on a boat in open water when a thunderstorm rolls in, return to shore immediately and seek shelter. If you are unable to return to shore, boats with cabins offer some protection. If caught in a storm in a small boat with no cabin, drop anchor and get as low as possible.

• Don’t stay in open vehicles.
  During a thunderstorm, avoid open vehicles such as convertibles, motorcycles, and golf carts.

• Don’t stay in open structures.
  Avoid open structures such as porches, gazebos, baseball dugouts, and sports arenas. These structures won’t protect you from lightning.
• Avoid open spaces.
  Stay away from open spaces such as golf courses, parks, playgrounds, ponds, lakes, swimming pools, and beaches. Seek shelter immediately.
• Don’t stay near tall structures.
  Stay away from tall structures, such as telephone poles and trees; lightning tends to strike the tallest object around.

Lightning: What You Need to Know

• NO PLACE outside is safe when thunderstorms are in the area!!
• If you hear thunder, lightning is close enough to strike you.
• When you hear thunder, immediately move to safe shelter: a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.
• Stay in safe shelter at least 30 minutes after you hear the last sound of thunder.

Indoor Lightning Safety

• Stay off corded phones, computers and other electrical equipment that put you in direct contact with electricity.
• Avoid plumbing, including sinks, baths and faucets.
• Stay away from windows and doors, and stay off porches.
• Do not lie on concrete floors, and do not lean against concrete walls.

Last Resort Outdoor Risk Reduction Tips

If you are caught outside with no safe shelter anywhere nearby the following actions may reduce your risk:

• Immediately get off elevated areas such as hills, mountain ridges or peaks
• Never lie flat on the ground
• Never shelter under an isolated tree
• Never use a cliff or rocky overhang for shelter
• Immediately get out and away from ponds, lakes and other bodies of water
• Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.)

People who work outdoors in open spaces, on or near tall objects, or near materials that conduct electricity are at high risk for being struck by lightning. Learn steps you can take to protect yourself from lightning while on the job.

People Who Work Outside are at Higher Risk

People at greatest risk of being struck by lightning are those who work outside or engage in outdoor recreational activities.

The following occupations have the highest risk of lightning strikes:

• Construction and building maintenance
• Roofing
• Farming and field labor
• Logging
• Explosives handling or storage
• Heavy equipment operation
• Pipefitting or plumbing
• Telecommunications field repair
• Power utility field repair
• Landscaping
• Airport ground personnel
• Pool and beach lifeguarding

Take Steps to Protect Yourself

If you work in high-risk occupations, you can take steps to protect yourself from lightning.

• Check the forecast
  Know the daily weather forecast so you are prepared and know what weather to expect during the day.

• Watch for signs of potential lightning strikes
  Pay attention to early weather signs of potential lightning strikes, such as high winds, dark clouds, or distant thunder or lightning. When these occur, don’t start any activity that you can’t quickly stop.
• Follow your company’s safety program
  Know your company’s lightning safety warning program, if it has one. These programs should include access to a safe location and danger warnings that can be issued in time for everyone to get to the safe location.

• Assess the threat
  Although no place outside is safe during a storm, you can minimize your risk by assessing the lightning threat early and taking appropriate actions. For example, if you hear thunder, lightning is close enough to strike you. Stop what you are doing and seek safety in a building or hard-top vehicle with the windows rolled up. When lightning strikes a hard-top metal vehicle, it goes through the metal frame, through the tires, and into the ground.

• Avoid tall structures
  Avoid anything tall or high, including rooftops, scaffolding, utility poles, cell phone towers, ladders, trees, and large equipment, such as bulldozers, cranes, and tractors.

• Avoid conductive materials
  Do NOT touch materials or surfaces that conduct electricity, including metal scaffolding, metal equipment, utility lines, water, water pipes, or plumbing.

• Stay away from explosives
  If you are in an area with explosives, leave immediately.

When thunder roars, go indoors!

If you hear thunder, even a distant rumble, get to a safe place immediately.

Call 911 if someone is struck by lightning

If your coworker is struck by lightning, call 911. Immediately begin first aid, if necessary. People who have been struck by lightning DO NOT carry an electrical charge and can be handled safely.

If you are caught in a lightning storm while camping, hiking, playing sports, or during other outdoor activities, it is often difficult to find a protected place. However, you can avoid lightning injuries by taking certain precautions.

• Check the forecast
  Before participating in outdoor activities, always check the weather forecast. Thunderstorms with lightning in the mountains occur most often during the summer months, in the late afternoon or evening. If you are heading to the beach or other water-related activities, check the forecast to know what to expect during the day.
• When thunder roars, go indoors
  Find a safe, enclosed shelter when you hear thunder. Even if you see blue sky, you could still be in danger. Tents, picnic shelters, gazebos, baseball dugouts, and other open shelters DO NOT provide protection from lightning. Don’t resume outdoor activities for at least 30 minutes after the storm. The beginning and the end of a storm are the most dangerous times.
• Seek shelter immediately, even if caught in the open
  If you are caught in an open area, act quickly to find adequate shelter. The most important action is to remove yourself from danger. Crouching or getting low to the ground can reduce your chances of being struck, but it does not remove you from danger.
• If you are caught outside with no safe shelter nearby, the following actions could reduce your risk of being struck by lightning:

  If you are caught in an open area, Do NOT lie down. Lightning causes electric currents along the top of the ground that can be deadly more than 100 feet away.

  • Immediately get off elevated areas such as hills, mountain ridges, or peaks.
  • Never lie flat on the ground. Crouch down in a ball-like position with your head tucked and hands over your ears so that you are down low, with minimal contact with the ground.
  • Never shelter under an isolated tree. If you are in a forest, shelter near lower trees.
  • Never use a cliff or rocky overhang for shelter.
  • Immediately get out of and away from ponds, lakes, and other bodies of water.
  • Stay away from objects that conduct electricity, such as barbed wire fences, power lines, or windmills.

• Separate from others
  If you are in a group during a thunderstorm, separate from each other. This will reduce the number of injuries if lightning strikes the ground.

• Don’t carry metal
  Don’t carry any metal objects, such as golf clubs, fishing poles, umbrellas, or backpacks with metal frames. Metal doesn’t attract electricity, but it is a good conductor. Your chances of a direct hit are higher when you are carrying a conductor above shoulder level. Be sure to avoid other metal objects as well, such as wire fences. You are more likely to be burned if you are in contact with metal when you are struck by lightning.

Did You Know?

The best place for shelter during a storm is inside a structure with four walls and a roof or an enclosed vehicle. Small, open shelters and tents do not provide protection. Large caves and valleys are protective. Small caves, overhangs, and wet stream beds are likely to be more dangerous than open areas because water conducts electricity and electricity can jump gaps between rocks.

Lightning is the most frequent weather hazard affecting athletic events, such as baseball, football, soccer, skiing, and track and field. Lightning can strike and injure players and spectators in outdoor stadiums during a sporting event.

Lightning Safety Action Plans

Large outdoor stadiums should have action plans and procedures for lightning safety. These plans should include the following:

• An evacuation plan for players and spectators
• A person monitoring all weather forecasts and reports
• A safe shelter

Evacuation plans should include specific evacuation directions for stadium personnel to communicate to fans. This will help avoid or reduce confusion. Evacuation procedures also should be posted on tickets, flyers, large screens, and posters to increase awareness.

Precautions

If you are attending an organized sporting event at an outdoor stadium during a thunderstorm, you can minimize your risk of being struck by lightning by taking precautions:

• Remain calm.
• Listen for instructions from stadium personnel.
• Move to the designated safe shelters, away from metal poles and the open field. These shelters should be determined before the event if a chance of a storm exists.
• Wait for an all-clear signal, which should occur approximately 30 minutes after you hear the last clap of thunder.

Learn steps you can take to protect yourself and your loved ones from lightning while participating in water activities.

• Check the forecast
  Before leaving for the beach or any water activity, such as a boating trip, check the weather forecast so you know what to expect during the day. If the forecast is for thunderstorms, plan your trip for another day.
• Go indoors
  Remember the phrase, “When thunder roars, go indoors.” If you hear thunder while you are at the beach, find a safe, enclosed shelter, such as your car. Do NOT seek shelter under beach picnic shelters.
• Listen to the forecast
  It is crucial to listen to weather information when you are at the beach or boating. Short-term forecasts are quite accurate, but sometimes miss some very localized storms.
• Learn how to read the weather
  Watch for the development of large, well-defined rising cumulus clouds. Cumulus clouds have flat bases and dome or cauliflower shapes. Cumulus clouds can develop into thunderstorms. Once the clouds reach 30,000 feet, the thunderstorm is generally developing, and it is time to head for shore. As clouds become darker and more anvil-shaped, the storm is already in progress.
• Watch and listen for distant storm activity
  Watch for distant lightning and listen for distant thunder. You might hear thunder before you see lightning on a bright day. If you hear thunder or see lightning, seek shelter away from the water.
• If you are out in the open water and a storm rolls in, return to shore immediately
  If you are on a boat in open water when a thunderstorm rolls in, return to shore immediately and seek shelter. Once on land, get at least 100 yards away from shore. If you are unable to return to shore, boats with cabins offer some protection. When inside the cabin during a lightning storm, stay away from all metal and electrical components, including the radio, unless it is an emergency. If caught in a storm in a small boat with no cabin, drop anchor and get as low as possible.
• Protect your boat
  The National Ag Safety Database provides a number of ways you can protect your boat and minimize damage if it is struck by lightning or is near a lightning strike.

Your pets cannot protect themselves from lightning; it is your responsibility to help protect them.

Take these steps to help protect your pet from lightning:

• Don’t leave your pet outdoors
  Do NOT leave your pet outdoors or chained to a tree during a lightning storm. Doghouses are NOT safe shelters; bring your pet inside.
• Remove any metal collars, leashes, or harnesses and replace with plastic
  Even though metal does not attract electricity, it is a good conductor and can make injuries, such as burns, worse if struck.

Myth: If you're caught outside during a thunderstorm, you should crouch down to reduce your risk of being struck.
Fact: Crouching doesn't make you any safer outdoors. Run to a substantial building or hard topped vehicle. If you are too far to run to one of these options, you have no good alternative. You are NOT safe anywhere outdoors.

Myth: Lightning never strikes the same place twice.
Fact: Lightning often strikes the same place repeatedly, especially if it's a tall, pointy, isolated object. The Empire State Building is hit an average of 23 times a year

Myth: If it’s not raining or there aren’t clouds overhead, you’re safe from lightning.
Fact: Lightning often strikes more than three miles from the center of the thunderstorm, far outside the rain or thunderstorm cloud. “Bolts from the blue” can strike 10-15 miles from the thunderstorm.

Myth: Rubber tires on a car protect you from lightning by insulating you from the ground.
Fact: Most cars are safe from lightning, but it is the metal roof and metal sides that protect you, NOT the rubber tires. Remember, convertibles, motorcycles, bicycles, open-shelled outdoor recreational vehicles and cars with fiberglass shells offer no protection from lightning. When lightning strikes a vehicle, it goes through the metal frame into the ground. Don't lean on doors during a thunderstorm.

Myth: A lightning victim is electrified. If you touch them, you’ll be electrocuted.
Fact: The human body does not store electricity. It is perfectly safe to touch a lightning victim to give them first aid. This is the most chilling of lightning Myths. Imagine if someone died because people were afraid to give CPR!

Myth: If outside in a thunderstorm, you should seek shelter under a tree to stay dry.
Fact: Being underneath a tree is the second leading cause of lightning casualties. Better to get wet than fried!

Myth: If you are in a house, you are 100% safe from lightning.
Fact: A house is a safe place to be during a thunderstorm as long as you avoid anything that conducts electricity. This means staying off corded phones, electrical appliances, wires, TV cables, computers, plumbing, metal doors and windows. Windows are hazardous for two reasons: wind generated during a thunderstorm can blow objects into the window, breaking it and causing glass to shatter and second, in older homes, in rare instances, lightning can come in cracks in the sides of windows.

Myth: If thunderstorms threaten while you are outside playing a game, it is okay to finish it before seeking shelter.
Fact: Many lightning casualties occur because people do not seek shelter soon enough. No game is worth death or life-long injuries. Seek proper shelter immediately if you hear thunder. Adults are responsible for the safety of children.

Myth: Structures with metal, or metal on the body (jewelry, cell phones,Mp3 players, watches, etc), attract lightning.
Fact: Height, pointy shape, and isolation are the dominant factors controlling where a lightning bolt will strike. The presence of metal makes absolutely no difference on where lightning strikes. Mountains are made of stone but get struck by lightning many times a year. When lightning threatens, take proper protective action immediately by seeking a safe shelter – don’t waste time removing metal. While metal does not attract lightning, it does conduct it so stay away from metal fences, railing, bleachers, etc.

Myth: If trapped outside and lightning is about to strike, I should lie flat on the ground.
Fact: Lying flat increases your chance of being affected by potentially deadly ground current. If you are caught outside in a thunderstorm, you keep moving toward a safe shelter.

Myth: lightning flashes are 3-4 km apart
Fact: Old data said successive flashes were on the order of 3-4 km apart. New data shows half the flashes are about 9 km apart. The National Severe Storms Laboratory report concludes: "It appears the safety rules need to be modified to increase the distance from a previous flash which can be considered to be relatively safe, to at least 10 to 13 km (6 to 8 miles). In the past, 3 to 5 km (2-3 miles) was as used in lightning safety education." Source: Separation Between Successive Lightning Flashes in Different Storms Systems: 1998, Lopez & Holle, from Proceedings 1998 Intl Lightning Detection Conference, Tucson AZ, November 1998.

Myth: A High Percentage of Lightning Flashes Are Forked.
Fact: Many cloud-to-ground lightning flashes have forked or multiple attachment points to earth. Tests carried out in the US and Japan verify this finding in at least half of negative flashes and more than 70% of positive flashes. Many lightning detectors cannot acquire accurate information about these multiple ground lightning attachments. Source: Termination of Multiple Stroke Flashes Observed by Electro- Magnetic Field: 1998, Ishii, et al. Proceedings 1998 Int'l Lightning Protection Conference, Birmingham UK, Sept. 1998.

Myth: Lightning Can Spread out Some 60 Feet After Striking Earth.
Fact: Radial horizontal arcing has been measured at least 20 m. from the point where lightning hits ground. Depending on soils characteristics, safe conditions for people and equipment near lightning termination points (ground rods) may need to be re-evaluated. Source: 1993 Triggered Lightning Test Program: Environments Within 20 meters of the Lightning Channel and Small Are Temporary Protection Concepts: 1993, SAND94-0311, Sandia Natl Lab, Albuquerque NM.

Lightning Trivia

• Cape Canaveral Air Force Station/Kennedy Space Center has documented lightning traveling almost 90 miles outward in the thunderstorm anvil.
• How far can you see lightning? According to Cape Canaveral/Kennedy Space Center, up to 100-km flashes.
• Lightning Causes Forest Fires. Can Forest Fires Cause Lightning? Yes, smoke and carbon micro-particles, when introduced into the upper atmosphere, can become the initiators of static. Sufficient atmospheric static can spark discharge as lightning. Reports of massive lightning storms in coastal Brasil, Peru and Hawaii have been linked to burning of sugar cane fields. The late 90's Mexican forest fires resulted in unusual lightning activity in the USA High Plains area (Lyons, et al.) So too can dust in an enclosed grain elevator create a static discharge. Recent reports (Orville, et al) show the Houston TX petrochemical industry, discharging copious amounts of hydrocarbons into the upper atmosphere, may be responsible for higher-than-normal lightning activity in that area. (National Lightning Safety Institute)

What is lightning?

Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground. In the early stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground. When the opposite charges build up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning. (The actual breakdown process is still poorly understood.) The air breakdown creates ions and free electrons that travel down the conducting channel. This current flow temporarily equalizes the charged regions in the atmosphere until the opposite charges build up again.

Lightning from thunderstorms begins in a strong electric field between opposite charges within the storm cloud, and can stay completely within the cloud (intra-cloud lightning) when the charge regions are similar strength (balanced) or can reach the ground (cloud-to-ground lightning) when one of the regions is much stronger than the other (unbalanced).

Lightning is one of the oldest observed natural phenomena on earth. It can be seen in volcanic eruptions, extremely intense forest fires (pyrocumulonimbus clouds), surface nuclear detonations, heavy snowstorms, in large hurricanes, and obviously, thunderstorms.

What are cloud flashes?

A cloud flash is lightning that occurs inside the cloud, travels from one part of a cloud to another, and some channels may extend into clear air.

What is a “stepped leader?”

A stepped leader is the development of the downward lightning channel. Negatively-charged lightning channels in particular do not propagate continuously, but in relatively short “steps” where the air ahead is becoming ionized as multiple low-conductivity “streamers.” A streamer that develops more current and better conductivity can become the next step that connects to the “leader” channel.

Is it possible to have thunder without lightning?

No, it is not possible to have thunder without lightning. Thunder starts as a shockwave from the explosively expanding lightning channel when a large current causes rapid heating. However, it is possible that you might see lightning and not hear the thunder because it was too far away. Sometimes this is called “heat lightning” because it occurs most often in the summer.

Is lightning always produced by a thunderstorm?

Thunderstorms always have lightning (thunder is caused by lightning, and you can't have a thunderstorm without thunder!), but you can have lightning without a thunderstorm. Lightning can also be seen in volcanic eruptions surface nuclear detonations, and in heavy snowstorms (“thunder snow”).

What causes thunder?

Thunder is caused by lightning. The bright light of the lightning flash caused by the return stroke mentioned above represents a great deal of energy. This energy heats the air in the channel to above 50,000° F in only a few millionths of a second! The air that is now heated to such a high temperature had no time to expand, so it is now at a very high pressure. The high pressure air then expands outward into the surrounding air compressing it and causing a disturbance that propagates in all directions away from the stroke. The disturbance is a shock wave for the first 10 yards, after which it becomes an ordinary sound wave, or thunder.

Fun fact: thunder can seem like it goes on and on because each point along the channel produces a shock wave and sound wave, so what you hear as thunder is actually an accumulation of multiple sound waves from the different portions of the lightning channel.

What is dry lightning?

Dry lightning is lightning that occurs without rain nearby. The NOAA Storm Prediction Center routinely issues forecasts for dry lightning because this kind is more likely to cause forest fires.

What is a “bolt from the blue”?

A “bolt from the blue” is a cloud-to-ground flash which typically comes out of the side of the thunderstorm cloud, travels a relatively large distance in clear air away from the storm cloud, and then angles down and strikes the ground. These lightning flashes have been documented to travel several miles away from the thunderstorm cloud. They can be especially dangerous because they appear to come from clear blue sky.

A helmeted bicyclist experienced a lightning strike to the head under fair weather conditions with a cloudless sky. It was determined that the bolt probably originated in a thunderstorm that was about 16km (approximately ten miles) away and obscured by mountains.

Does lightning always strike the tallest object?

Never say always! Lightning usually strikes the tallest object. It makes sense that the tallest object is most likely to produce upward streamers to connect with the downward lightning leader.

What type of electricity is lightning?

Lightning is an electrostatic discharge accompanied by the emission of visible light and other forms of electromagnetic radiation.

How many volts and watts are in lightning?

Lightning can have 100 million to 1 billion volts, and contains billions of watts.

Why are positive lightning bolts deemed more dangerous than the more common negatively charged bolts?

You don’t want to run into either, but positive lightning may be considered more dangerous because its peak electric current is often stronger, the flash duration (continuing) is typically longer, and its peak charge can be much greater than a negative strike. The longer-duration current is thought to make it more likely to ignite fires, as well.

Does lightning strike from the sky down, or the ground up?

The answer is both. Cloud-to-ground (CG) lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge under a typical thunderstorm. (The charge that builds up in a small area of the Earth’s surface and the objects on it is determined by the net charge above it since the Earth’s surface is relatively conductive and can move charge in response to the thunderstorm.) Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast - in a few thousandths of a second - so the human eye doesn't see the actual formation of the stroke. Natural lightning can also trigger upward discharges from tall towers, like broadcast antennas. For more information on cloud-to-ground (and other types of lightning) visit the Severe Weather 101: Lightning Types page.

How hot can lightning make the air?

Energy from lightning heats the surrounding air anywhere from 18,000 degrees Fahrenheit to up to 60,000 degrees Fahrenheit.

What causes lightning to be colored rather than the usual white or blue?

Lightning can appear to be many different colors depending on what the light travels through to get to your eyes. In snowstorms, where it is somewhat rare, pink and green are often described as colors of lightning. Haze, dust, moisture, raindrops and any other particles in the atmosphere will affect the color by absorbing or diffracting a portion of the white light of lightning.

How does the Earth benefit from lightning?

The earth benefits from lightning in several ways. First, thunderstorms and lightning are part of the Earth’s global electric circuit. Thunderstorms and electrified clouds are like batteries that cause the Earth to have negative charge and the atmosphere to have positive charge.. This maintains the fair weather electric field, which is about 100 V/m near the surface. There is always a steady current of negatively-charged ions flowing upwards from the entire surface of the Earth (and positive ions downward from the atmosphere). Thunderstorms help transfer the negative charges back to Earth (lightning is generally negatively charged). Without thunderstorms and lightning, the earth-atmosphere electrical balance would disappear in 5 minutes. Lightning also makes ozone-producing chemicals.

What happens to the ground when lightning strikes it?

What tends to happen when lightning strikes ground is that it fuses dirt and clays in to silicas. The result is often a glassy rock (called a fulgurite) in the shape of a convoluted tube. Fulgurite has been found all over the world, but is relatively rare. The color depends on the minerals in the sand that was struck.The shape in the ground is the shape of the path the lightning current followed in the ground. There is often damage to grasses along this path too.

Lightning traveling down a tree trunk turns water to steam. If it gets under the bark into the surface moisture of the wood, the rapidly expanding steam can blast pieces of bark and branches from the tree, and the wood along the path is often killed. The charge carried by the lightning is then dissipated along the surface of the Earth. If you are near something that was hit by lightning such as a tree or fence, this process can be very dangerous as all of this current does not get dissipated instantaneously. The lightning may hit a tree then branch off and hit something else, or after the current travels through the tree trunk, it can also travel through the immediately surrounding area, and into anything or anyone nearby. This process, however, is fairly quick, so the ground or whatever was struck does not remain electrically dangerous afterwards.

The lightning current can travel even farther through water, metal fences, power lines or plumbing. Lightning current may enter a building and transfer through wires or plumbing and damage everything in its path. Similarly, in urban areas, it may strike a pole or tree and the current then travels to several nearby houses and other structures and enter them through wiring or plumbing.

Can lightning strike the same place twice?

Lightning does hit the same spot (or almost the same spot) more than once, contrary to folk wisdom. It could be simply a statistical fluke (i.e., with all the lightning that occurs, eventually lightning will strike somewhere near a previous lightning strike within a short period of time). It could also be that something about the site makes it somewhat more likely to be struck. Typically, when lightning strikes something on the ground, the object that is struck sends a faint channel upward that joins the downward developing flash and creates the connection to the ground. Taller objects are more likely than shorter objects to produce the upward channel. But it is also possible that something that locally affects the ability of the ground to conduct electricity (such as the salt or moisture content of the ground at the time, the presence or absence of rock, standing water, pipes or other metal objects in the ground), the terrain shape, the shape of leaves or twigs, or something else might make a particular location more likely than another nearby location to be struck.

When and where does lightning most frequently strike?

Lightning comes from a parent cumulonimbus cloud. These thunderstorm clouds are formed wherever there is enough upward air motion, convective instability, and moisture to produce a deep cloud that reaches up to levels colder than freezing.

These conditions are most often met in the warm seasons (spring, summer, early autumn). In general, the US mainland has a decreasing amount of lightning toward the northwest. Over the entire year, the highest frequency of cloud-to-ground lightning is in Florida between Tampa and Orlando. This is due to the presence, on many days during the year, of a large moisture content in the atmosphere at low levels (below 5,000 feet), as well as high surface temperatures that produce strong sea breezes along the Florida coasts. The western mountains of the US also produce strong upward motions and contribute to frequent cloud-to-ground lightning. There are also high frequencies along the Gulf of Mexico coast, the Atlantic coast in the southeast US, and inland from the Gulf. Regions along the Pacific west coast have the least cloud-to-ground lightning.

How do storms become electrified?

Clouds become electrified when strong updrafts (fueled by convective instability and moisture) produce a mixture of larger ice particles (graupel), small ice crystals, and supercooled liquid water drops and ice crystals at temperatures less than freezing (0 deg C). In this environment, rebounding collisions between the graupel ice crystals cause charge to be transferred between the particles. This is called the noninductive process because it does not require a pre-existing electric field to polarize the particles. The exact physical mechanisms are not completely understood, but it involves a transfer of mass from one particle to the other, and the sign of charge is dependent on temperature and the growth rates of the particles. The graupel and crystals gain opposite signs of charge, and then they form separate charge regions as the graupel fall faster in the updraft.

A secondary process may occur when electric fields increase and cause droplets to become polarized (ions within droplets driven by the electric field to oppose sides of the droplet). If part of the droplet freezes onto an ice particle and the rest breaks away, some net charge of ions from the drop can be captured by the ice. This is known as an inductive process since it requires an appreciable electric field to occur.

Does lightning happen during the winter?

Lightning occurs less frequently in the winter because there is not as much instability and moisture in the atmosphere as there is in the summer. These two ingredients work together to make convective storms that can produce lightning. Without instability and moisture, strong thunderstorms are unlikely.

During the winter, the land surface is cooler because there is not as much heating by the sun to warm it up. Without warm surface temperatures, the near-surface air wouldn't rise in the atmosphere very far. Thus, the kinds of deep (8-15 km deep) thunderstorms that develop in the summertime wouldn't develop.

Warm air holds more water vapor. And, when water vapor condenses into liquid water cloud drops, latent heat is released which fuels the thunderstorm. So, warm, moist air near the surface (and the proper conditions aloft to give you lots of instability) can result in deep convection, which may produce lightning discharges.

What is thundersnow?

Although thunderstorms are less common in the winter, sometimes lightning can occur within snowstorms. Called thundersnow, relatively strong instability and abundant moisture may be found above the surface, such as above a warm front, rather than at the surface where it may be below freezing. Thundersnow is sometimes observed downstream of the Great Salt Lake and the Great Lakes during lake-effect snowstorms, too.

How many flashes a year are there?

Over the contiguous 48 states, an average of 20,000,000 cloud-to-ground flashes have been detected every year since the lightning detection network (NLDN) covered all of the continental US in 1989. In addition, about half of all flashes have more than one ground strike point, so at least 30 million points on the ground are struck on the average each year in the US. Besides cloud-to-ground flashes, there are roughly 5 to 10 times as many cloud flashes as there are ground flashes.

How can I stay safe from lightning?

NOAA's National Weather Service is an excellent source for information on indoor and outdoor lightning safety and lightning risks.

What are the odds of being struck by lightning?

According to the NWS, the chance of an individual in the U.S. being struck during a given year is one in 1.2 million. The odds of being struck in your lifetime (estimated to be 80 years) are 1 in 15,300. You can read more about where these numbers come from on the National Weather Service website. A lot depends on your exposure, however. You can reduce your risk of being struck by lightning by going to a good shelter such as an enclosed building (see link above) if there is a thunderstorm near you! The most dangerous times of a storm can be the beginning and end of lightning production. If the first flash is a CG, it will come without any warning from previous thunder. The last flash of a storm may come many minutes after the next-to-last flash, so it is important to wait long enough for conditions to be safe again.

Where can I get information on lightning strikes that occur in my area?

There are several companies that collect and archive this data including Vaisala and Earth Networks which operate networks in the United States. We actually purchase lightning data ourselves (we do not have the funds to maintain our own network) and have strict rules about how we can use it.

How can I protect myself from a lightning strike?

Be prepared. Check the weather before participating in outdoor activities. If thunderstorms are forecast, change plans or ensure that a safe shelter is nearby.

If inside during a thunderstorm, do the following:

• Stay off corded phones. Cell phones and cordless phones are okay.
• Do NOT use anything connected to an electrical outlet, such as computers or other electronic equipment.
• Stay out of the shower and away from other plumbing. This includes washing dishes.
• Stay away from windows and doors.

If outside during a thunderstorm, do the following:

• Seek shelter immediately.
• Do NOT lie on the ground or shelter under a tree.
• If no shelter is nearby, crouch down into a ball-like position with your head tucked and hands over your ears and your feet closely together.

What is considered a safe shelter during a lightning storm?

A safe shelter is a fully enclosed vehicle or a shelter that has four walls and a roof. Examples of safe shelters include homes, offices, shopping centers, and hard-top vehicles with the windows rolled up. Open vehicles (such as convertibles, golf carts, and motorcycles) and open structures (such as porches, gazebos, baseball dugouts, and sports arenas) are NOT safe during a storm.

Can I get struck by lightning if there is no rain?

Yes. Even if you don’t see rain, you could still be at risk for a lightning strike. Lightning often strikes outside areas of heavy rain and can strike as far as 10 miles away from any rainfall. Many lightning deaths occur ahead of storms or after storms seemingly have passed. Remember, if you can hear thunder, you might be in danger of a lightning strike.

Does lightning ever strike the same place twice?

Yes. Lightning can strike the same place twice. In fact, lightning often strikes the same place repeatedly, especially a tall, pointy, isolated object. For example, the Empire State Building is hit by lightning about 23 times a year.

What should I do if I am inside during a thunderstorm?

To stay safe inside a building, do the following:

• Stay away from electrical equipment or cords, including corded phones.
• Avoid plumbing; do NOT wash your hands, take a shower, or wash dishes.
• Stay away from windows and doors, and stay off porches and balconies.
• Do NOT lie down on concrete floors or lean against concrete walls.

Is it safe to take a shower or bath during a thunderstorm?

No. Lightning can travel through plumbing. It is best to avoid all water during a thunderstorm. Do not shower, bathe, wash dishes, or wash your hands. The risk of lightning travelling through plumbing might be less with plastic pipes than with metal pipes. However, it is best to avoid any contact with plumbing and running water during a lightning storm to reduce your risk of being struck.

Are cell phones and cordless phones safe to use during a thunderstorm?

Yes. Cell phones and cordless phones are safe to use during a thunderstorm if they are not connected to an outlet through a charger. Do not use corded phones.

What should I do if I am caught outside during a thunderstorm?

Do NOT lie on the ground. Lightning causes electric currents along the top of the ground that can be deadly more than 100 feet away. Get inside a safe location; no place outside is safe. Avoid anything that will increase your risk of being struck by lightning, such as being near or under tall trees. If there are no safe shelters in sight, crouch down in a ball-like position: put your feet together, squat low, tuck your head, and cover your ears. But remember, this is a last resort. Seek safe shelter first.

Is it safe to be under a tree during a lightning storm?

No. Being underneath trees is the second leading cause for lightning deaths.