Lightning Safety

Lightning and Lightning Safety - An Introduction

Maine ranks 41st in lightning casualties in the US, according to 2013-2022 data from the Lightning Safety Council.

In the United States, there are between 20 and 25 million cloud-to-ground lightning flashes each year. Maine averages about 60,000 flashes each year. While lightning can be fascinating to watch, it is also extremely dangerous. Each one of those 25 million flashes is a potential killer. According to the National Weather Service, lightning kills about 20 people in the United States each year, with hundreds severely injured. 

Lightning causes considerable damage

In addition to the deaths and injuries, lightning causes considerable damage across the nation. Each year, lightning is the cause of about 25,000 fires, including about 4400 house fires, 1800 other structural fires, and numerous forest fires. Those fires are responsible for an additional estimated 12 deaths per year. All totaled, lightning causes nearly $1 billion in damages each year.


  • Plan outdoor activities to avoid thunderstorms
  • Monitor weather conditions. If you hear thunder, get inside a substantial building immediately.
  • If a substantial building is not available, get inside a hard-topped metal vehicle. If the vehicle is struck, the lightning will follow the outer metal shell of the vehicle to the ground. It's important to make sure that you're fully inside the vehicle with the windows rolled up. Note that the rubber tires do not prevent the vehicle from being struck, nor do they provide any protection.
  • Avoid open areas and stay away from isolated tall objects.


  • Avoid contact with any equipment connected to electrical power, such as computers or appliances.
  • Avoid contact with water or plumbing.
  • Stay off corded phones.
  • Stay away from windows and doors.
  • Remain inside for 30 minutes after the last rumble of thunder is heard.

Remember - There is no safe place outside during a thunderstorm. When thunder roars, go indoors!

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Lightning Safety around the Home

Although houses and other substantial building offer the best protection from lightning, each year many homes across the United States are struck by lightning. In fact, on average, lightning causes about 4400 house fires and 1800 other structural fires each year, some of which are deadly. All totaled, lightning causes nearly $1 billion in damages each year.

There are three main ways lightning enters homes and buildings: (1) a direct strike, (2) through wires or pipes that extend outside the structure, and (3) through the ground. Regardless of the method of entrance, once in a structure, the lightning can travel through the electrical and phone wires, the plumbing, and/or radio and television reception systems. Lightning can also travel through any metal wires or bars in concrete walls or flooring.

Indoor safety depends on avoiding contact with items that could conduct lightning within the home. Here are some indoor safety tips to follow when a thunderstorm is in the area:

  • 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.

In case your home is struck by lightning:

  • Evacuate your home immediately if you smell smoke and call 911.
  • Call your local fire department and, if possible, have them check for hot spots in your walls with thermal imaging equipment.
  • Make sure all smoke detectors are powered and operating properly.
  • If needed, have a licensed electrician check the wiring in your home.

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Lightning Safety at Work

Do you work outside during the summer?

For those who work outside during the summer, lightning is a potentially deadly threat. While summer is a good time to complete outside work, it is very important to work in a safe environment. Any time a thunderstorm is in the area, no place outside is safe. Between 2006 and 2017, 65 people were struck and killed by lightning in the United States while at work. About two-thirds of those killed were farmers, ranchers, roofers, lawn care workers, or construction workers. Many of those killed were seeking shelter at the time of the deadly strike, but just hadn't started soon enough.

When thunderstorms threaten, don't start anything you can't quickly stop. Pay attention to the daily forecasts so you know what to expect during the day. Also pay attention to early signs of thunderstorms: high winds, dark clouds, rain, distant thunder or lightning. If these conditions exist, do not start a task you cannot quickly stop. If you can hear thunder, lightning is close enough to strike. Stop what you are doing and seek safety in a substantial building or a hard-topped metal vehicle. When Thunder Roars, Go Indoors!

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Lightning Safety and Sports Activities

Whether you're out kicking a ball around with a friend, or at a major sports event, you should be prepared to get to a safe place in case a thunderstorm threatens. Since 2006, sports activities (golf, soccer, running, baseball, football) contributed to 31 lightning deaths in the United States. In many cases, those involved in the activities failed to realize the developing danger.

For anyone outside, whether you're involved in sports or some other activity, keep an eye on the sky and head to safety at the first sign of a developing or approaching storm. If you hear thunder, you're already in danger and should head inside a substantial building or hard-topped vehicle immediately.

Officials in charge of organized sports should have a lightning safety plan, and those involved in the sport (and their parents) should understand the plan and know what to do. The plan should include where the participants and spectators go for safety, when the event should be stopped, when the event should be resumed, and who is in charge of making weather-related safety decisions. It's also important to designate a person to monitor conditions and to keep those in charge informed of weather-related threats. The plan should also account for the time required to get everyone to safety.

For stadiums and larger venues, the National Weather Service has toolkits which provide templates to help design a safety plan. Those toolkits can be found at:

Whether you're out for a run, watching your child's game, or attending a major sports event, remember that there's no safe place outside in a thunderstorm. When thunder roars, go indoors!

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Lightning's Most Deadly Activities

Some activities are more dangerous than others

If you're outside when a thunderstorm is in the area, you're at risk of being struck and potentially killed or seriously injured by lightning. However, there are some activities that lead to more lightning deaths and injuries than others.

In the past twelve years, leisure activities led to almost two thirds of the lightning fatalities in the United States. Water-related activities, and particularly fishing, contributed most to the fatalities. Since 2006, 34 people who had been fishing died as a result of lightning. Boating and beach activities also contributed significantly to the death toll. In most cases, victims simply waited far too long before starting to seek shelter.

When it comes to water-related activities, there are several important things to remember.

  • Always have a plan so that you can get to a safe place before the storm arrives.
  • Head to that safe place immediately if you see any signs of a developing or approaching thunderstorm. Don't hesitate.

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Lightning: The Science

Understanding the Science of Thunderstorms and Lightning

Minimize your risk of becoming
a lightning victim: get to a safe
shelter sooner and stay there

By definition, all thunderstorms contain lightning. Lightning is a giant spark of electricity that occurs within the atmosphere or between the atmosphere and the ground. As lightning passes through the air, it heats the air rapidly to a temperature of about 50,000 degrees Fahrenheit, about 5 times hotter than the surface of the sun.

During a lightning discharge, the sudden heating of the air causes it to expand rapidly. After the discharge, the air contracts quickly as it cools back to a normal temperature. This rapid expansion and contraction of the air causes a shock wave that we hear as thunder (this shock wave can damage walls and break glass).

All thunderstorms go through various stages of growth, development, electrification, and dissipation. The process of thunderstorm development often begins 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 reach a certain level in the atmosphere, cumulus clouds start to form. Continued heating can cause these clouds to grow vertically upward into the atmosphere. These "towering cumulus" clouds may be one of the first indications 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 with mostly small ice crystals in the upper levels of the cloud, a mixture of small ice crystals and small hail (graupel) in the middle levels of the cloud, and a mixture of rain and melting hail in the lower levels of the cloud. Due to air movements and collisions between the precipitation particles near the middle of the cloud, the various precipitation particles become charged. The lighter ice crystals become positively charged and are carried upward into the upper part of the storm by the updraft. The heavier hail becomes negatively charged is suspended by the updraft or falls toward the lower part of the storm. The end result is that the top of the cloud becomes positively charged and the middle and lower part of the storm becomes negatively charged.

Normally, the earth's surface has a slight negative charge; however, as the negative charges build up in the lower and middle part of the storm, the ground beneath the base of the cloud and in the area immediately surrounding the cloud becomes positively charged. As the cloud moves, these induced positive charges on the ground follow the cloud like a shadow. Farther away from the cloud base, but under the positively charged anvil, the negative charge may be further induced.

In the initial stages of development, air acts as an insulator between the positive and negative charges. However, when the electrical potential between the positive and negative charges becomes too great, the insulating capacity of the air breaks down and there is a discharge of electricity that we know as lightning.

Lightning can occur completely within the thunderstorm cloud or between the cloud and the ground. In-cloud lightning generally occurs between positive charges near the top of the cloud and negative charges near the middle or bottom of the cloud. Cloud-to-ground lightning occurs between charges in the cloud and charges on the ground. Lightning can also occur between clouds.

Cloud-to-ground lightning can be categorized into two different types -- the negative flash and the positive flash. The negative flash usually occurs between the negative charges in the lower part of the storm and the positive charges on the ground under and near the cloud base. Positive flashes usually occur between the positively-charged upper levels of the storm and the negatively-charged area surrounding the storm.

In the negative cloud-to-ground flash, an almost invisible, negatively-charged channel of air forms in the lower part of the cloud and surges downward toward the ground. As this "step leader" approaches the ground, streamers of positive charge propagate upward from trees, buildings, and other objects on the ground. When one or more of these streamers meet the step leader, the connection is complete, and the lightning channel discharges which we see as the very bright "return stroke" that we call lightning. The entire process takes only a small fraction of a second.

The process for a positive flash is similar except that a positive channel usually originates in the anvil of the storm and propagates downward. In this case, streamers of negative charge move up to meet positively-charged channel as it approaches the ground. When a connection is made, a positive flash of lightning occurs.

While both negative and positive flashes of lightning can be deadly, positive flashes are more apt to catch people by surprise. Because the distance between the ground and anvil is much greater than the distance between the ground and the cloud base, a much larger electric potential is needed to initiate a positive flash of lightning. For the same reason, positive flashes are infrequent and widely scattered around the storm.

The greatest danger associated with the positive flashes, however, is that they strike in areas where most people think they are safe from the storm. They generally strike well beyond the area where rain is falling and well beyond the main area where most of the lightning (negative flashes) and thunder is occurring. Consequently, many victims are caught completely off guard.

The best advice in order to minimize your risk of becoming a lightning victim is to get to a safe shelter sooner and to stay there longer. In general, if you can hear thunder, you are within striking distance of the storm.

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Questions & Answers

The answers to these lightning questions have been provided by the National Weather Service.


How powerful is lightning and how fast does it move?


Lightning is a giant spark of electricity. A typical lightning flash contains about 30,000 amps and 300 million volts. This compares to a standard household current of 15 amps and about 120 volts. Typically, a lightning flash is only 1 to 2 inches wide. The step leader that initiates the lightning flash propagates downward from the cloud at a rate of about 320,000 ft per second or about 220,000 miles per hour. The return stroke (the current that cause the visible flash) moves upward at a speed of about 320,000,000 ft per second or about 220,000,000 miles per hour (about 1/3 the speed of light). In comparison, the sound of thunder travels at about 1100 ft per second or about 750 miles per hour.


How can you tell how far a flash of lightning is away from you?


While you see the visible flash of lightning almost instantaneously, the sound of the thunder travels at a speed of about 1100 feet per second or about 1 mile in 5 seconds. For every 5 seconds between the time you observe the lightning and the time you hear the thunder, the lightning flash is 1 mile away. If it takes 10 seconds between the lightning flash and the thunder, the lightning flash was 2 miles away. For 15 seconds, the flash would be three miles away. Unfortunately, this method only works for the previous flash and does not tell you how close the next lightning strike will be. Generally, if you hear thunder, you are within striking distance for the next flash of lightning. If you are not in a safe place at the time, move to a safe place immediately.


Are there any signs that a lightning strike is imminent?


Sometimes, but not always. In either case, there is little, if any, time to take action to protect yourself. Some of the signs include:

  1. Your hair stands on end (as charges from the ground surge to the top of your head)
  2. You hear a distinctive snapping or crackling sound (small discharges of static electricity may occur in an area where lightning is about to strike)
  3. You experience a tingling sensation (electrical charges may be moving through your body)
  4. There is a sudden increase in the static on portable electronic devices (electrical charges may be moving through the devices, and
  5. An abnormal burning smell in the air (static discharges within the air give off an unusual odor)

If you see any of these signs, lightning is about to strike you or somewhere very near you. It is extremely important that you plan ahead to avoid this situation. You could be killed at any instant.


Is it safe to talk on a cordless phone during a thunderstorm?


Compared to talking on a corded phone, the cordless phone is much less of a hazard. However, there is a momentary risk of being struck by lightning when the phone is being removed from the cradle. Once out of the cradle, it is safe to use a cordless phone during a thunderstorm, provided, of course, that you are in a safe place.


What are the chances that a person will be struck by lightning during his or her lifetime?


Based on documented cases of lightning deaths and injuries, the nationwide odds of being killed or injured by lightning are estimated to be about 1 in 400,000 for each year of your life. Assuming a life span of 80 years, that's lifetime odds of more than 1 in 12,000. Keep in mind, though, that your behavior around thunderstorms will determine your individual odds. If you are aware of all the threats posed by lightning and act accordingly, your chances for being struck by lightning will be considerably lower. On the other hand, if you are not aware of those dangers or don't take the appropriate safety precautions, your odds of being struck by lightning will be higher.


What do I do if someone is struck by lightning?


Lightning victims do not carry an electrical charge, are safe to touch, and may need immediate medical attention. Cardiac arrest is the immediate cause of death for those who die. Some deaths can be prevented with proper first aid. Call 911 and then give first aid. CPR and use of an AED (automatic external defibrillator) may be needed.

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