Thunder and Lightning: The Facts

All thunderstorms are dangerous, and every thunderstorm produces lightning. In the United States, an average of 300 people are injured and 80 people are killed each year by lightning. Although most lightning victims survive, people struck by lightning often report a variety of long-term, debilitating symptoms.

Other associated dangers of thunderstorms include tornadoes, strong winds, hail, and flash flooding. Flash flooding is responsible for more fatalities - more than 140 annually - than any other thunderstorm-associated hazard.

Dry thunderstorms that do not produce rain that reaches the ground are most prevalent in the western United States. Falling raindrops evaporate, but lightning can still reach the ground and can start wildfires.

Facts about thunderstorms:

• Warm, humid conditions are highly favorable for thunderstorm development.
• Thunderstorms may occur singly, in clusters, or in lines.
• Thunderstorms typically produce heavy rain for a brief period, anywhere from 30 minutes to an hour.
• Some of the most severe occur when a single thunderstorm affects one location for an extended time.
• About 10% of thunderstorms are classified as severe - this means they produce hail at least three-quarters of an inch in diameter, have winds of 58 miles per hour or higher, or produce a tornado.

Facts about lightning:

• Lightning's unpredictability increases the risk to individuals and property.
• Lightning often strikes outside of heavy rain and may occur as far as 10 miles away from any rainfall.
• Most lightning deaths and injuries occur when people are caught outdoors in the summer months during the afternoon and evening.
• "Heat lightning" is actually lightning from a thunderstorm too far away for thunder to be heard. However, the storm might be moving in your direction.
• Your chances of being struck by lightning are estimated to be 1 in 600,000, but could be reduced even further by following safety precautions.
• Lightning strike victims carry no electrical charge and should be attended to immediately.

Know the Terms
A Severe Thunderstorm Watch tells you when and where severe thunderstorms are likely to occur. Watch the sky and stay tuned to NOAA Weather Radio, commercial radio, or television for information.

A Severe Thunderstorm Warning is issued when severe weather has been reported by spotters or indicated by radar. Warnings indicate imminent danger to life and property to those in the path of the storm.

Take Protective Measures

Before the Storm
If a thunderstorm is likely in your area:

• Postpone outdoor activities.
• Get inside a home, building, or hard-top automobile (not a convertible). Although you can be injured if lightning strikes your car, you are much safer inside a vehicle than outside.
• Rubber-soled shoes and rubber tires provide NO protection from lightning. However, the steel frame of a hard-topped vehicle provides increased protection if you are not touching metal.
• Secure outdoor objects that could blow away or cause damage. Remove dead or rotting trees and branches that could fall and cause injury or damage during a severe thunderstorm.
• Shutter windows and secure outside doors. If shutters are not available, close window blinds, shades, or curtains.
• Avoid showering or bathing. Plumbing and bathroom fixtures can conduct electricity.
• Use a corded telephone only for emergencies. Cordless and cellular telephones are safe to use.
• Unplug appliances and other electrical items such as computers and turn off air conditioners. Power surges from lightning can cause serious damage.
• Use a battery-operated NOAA Weather Radio for updates from local officials.

Avoid the following:

• Natural lightning rods such as a tall, isolated tree in an open area.
• Hilltops, open fields, the beach, or a boat on the water.
• Isolated sheds or other small structures in open areas.
• Anything metal-tractors, farm equipment, motorcycles, golf carts, golf clubs, and bicycle.

During the Storm

If you are in a forest, seek shelter in a low area under a thick growth of small trees. In an open area, go to a low place such as a ravine or valley; but be alert for flash floods. If you are on open water, get to land and find shelter immediately.

If you ever feel your hair stand on end-which indicates that lightning is about to strike-squat low to the ground on the balls of your feet. Place your hands over your ears and your head between your knees. Make yourself the smallest target possible and minimize your contact with the ground.Do not lie flat on the ground.

After the Storm

If you are helping the victim of a lightning strike, first check the victim's breathing - if it has stopped, begin mouth-to-mouth resuscitation. Second, check the victim's heartbeat - if the heart has stopped, administer CPR. Third, check the pulse - if the victim has a pulse and is breathing, look for other possible injuries. Check for burns where the lightning entered and left the body. Also be alert for nervous system damage, broken bones, and loss of hearing and eyesight.

Remember the 30/30 lightning safety rule: Go indoors if, after seeing lightning, you cannot count to 30 before hearing thunder. Stay indoors for 30 minutes after hearing the last clap of thunder.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.