Lightning is found with every thunderstorm. While the lightning displays may be impressive to watch...they are also deadly! Lightning also causes several hundred million dollars in damage to homes, businesses, churches, barns, and forests each year.

A lightning bolt striking the ground in a large thunderstormHow Lightning Forms

Within the thunderstorm clouds, rising and falling air causes turbulence which results in a build-up of a static charge. The negative charges concentrate on the base of the cloud. Since like charges repel, some of the negative charges on the ground are pushed down away from the surface, leaving a net positive charge on the surface.

Opposite charges attract, so the positive and negative charges are pulled toward each other. This first, invisible stroke is called a stepped leader. As soon as the negative and positive parts of the stepped leader connect there is a conductive path from the cloud to the ground. The negative charges rush down it causing the visible stroke.

Flash to Bang

Thunder is caused by the extreme heat associated with the lightning flash. In less than a second, the air is heated to 15,000 to 60,000 degrees. When the air is heated to this temperature, it rapidly expands. When lightning strikes very close by, the sound will be a loud bang, crack or snap. The duration of the thunder associated with a nearby lightning strike will be very short. Lightning will rumble for a longer period of time as the sound arrives at different times. This is due to the length of the lightning flash (typically many miles long).

Thunder can typically be heard up to 10 miles away. During heavy rain and wind, this distance will be less, but on quiet nights, when the storm is many miles away, thunder can be heard at longer distances. Bang"

Estimating the Distance

You can estimate the distance to a thunderstorm using the "Flash to Bang." The time from seeing lightning until you hear thunder. Count the seconds between the lightning "flash" and the "bang" of thunder. Every five seconds equals one mile. If you count 15 seconds, the flash was 3 miles away and you know that you are in a high danger zone. Six miles is still in a high danger zone.

Lightning can strike many miles from the parent thunderstorm - so when should you seek a safe shelter? The best answer is also the easiest to remember.

If you can see it or if you can hear it, flee it!

Resuming Activity After a Thunderstorm

  • Wait at least 30 minutes after the last thunder is heard before going back outside. Most lightning deaths and injuries occur when people are caught outdoors. If caught outdoors during a thunderstorm and no shelter is nearby...find a low spot away from trees, fences, and poles. If you are in the woods, take shelter under the shorter trees.
  • If you are boating or swimming, get to land and find shelter immediately. You should also get out of open areas, such as golf courses, baseball diamonds and soccer fields during thunderstorms. Put your head bPhoto of two people with hair sticking straight up from the electrical charge after a stormetween your knees
  • If you feel your skin tingle or your hair stands on end, squat low to the ground on the balls of your feet. Places your hands on your knees with your head between them. Make yourself the smallest target possible and minimize your contact with the ground.
  • These two brothers didn’t recognize the danger they were in. Their hair is standing on end from a thunderstorm-induced electrical charge. The two brothers, and their sister, were killed moments later when lightning struck.

Myths & Facts

  • Myth: One myth about lightning is that people struck by lightning carry an electrical charge and shouldn’t be touched.
    • Fact: Lightning strike victims carry no electrical charge and should be attended to immediately! Call 911 or the local emergency number for advanced medical care immediately. CPR should be started if necessary. Contact your local American Red Cross for information on CPR and first aid classes.
  • Myth: If it isn’t raining, then there is no danger from lightning.
    • Fact:  Lightning often strikes outside of heavy rain and may occur as far as 10 miles from any rainfall!
  • Myth: The rubber soles of shoes or rubber tires on a car will protect you from being struck by lightning.
    • Fact: Rubber soles and rubber tires provide no protection from lightning. The steel frame of a hard-topped car provides increased protection if you aren’t touching metal. Although you may be injured if lightning strikes your car, you are much safer inside a car than outside.
  • Myth: "Heat lightning" occurs after a very hot summer day and poses no threat.
    • Fact: What is called "heat lightning" is actually lightning from a thunderstorm too far away for thunder to be heard; however, the storm may be heading in your direction!