Approximately 10% of thunderstorms are considered severe, which means they produce hail at least three-quarters of an inch in diameter, have winds of at least 58 miles per hour, or produce a tornado.
Lightning often strikes outside of heavy rain and may occur as far as ten miles from any rainfall. Most lightning deaths and injuries occur when people are caught outdoors in the summer months during the evening or afternoon.
The chances of being struck by lightning are about 1 in 600,000.
- Stay informed—listen to the radio or the Weather Network to check local forecasts and news reports regularly. Keep a battery-powered or hand-cranked radio along with extra batteries.
- Buy ground fault protectors for key electrical equipment.
- Remove dead or rotting trees and branches that could fall.
- If a thunderstorm is likely in your area, postpone outdoor activities.
- Shutter windows and secure outside doors and objects. Secure outdoor objects that could blow away.
- Unplug appliances and other electrical items, such as computers, and turn off air conditioners. If you are unable to unplug them, turn them off.
- Follow the 30-30 rule: When you see lightning, count the seconds until you hear thunder. If that time is 30 seconds or less, the thunderstorm is within 6 miles and is dangerous. Seek shelter immediately. The threat of lightning continues longer than most people think. Wait at least 30 minutes after the last thunder before leaving your shelter.
- If you can hear thunder, you are within striking distance for lightning. Seek safe shelter immediately.
- Stop outdoor activities at the first clap of thunder and get inside a large building or an enclosed vehicle. Wait 30 minutes after the thunder to go back outside.
- When inside, stay off corded phones, computers, and other electronic equipment that put you in direct contact with electricity or plumbing. Cordless phones and cell phones are safe to use. Avoid showering or bathing.
- If you are in open water, go to land and seek shelter immediately.
- If you feel your hair stand on end, indicating 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.
- If a person is struck by lightning, call 9-1-1 and get medical care immediately.
- Lightning strike victims carry no electrical charge; attend to them immediately. Check their breathing, heartbeat, and pulse.
Developed by NFPA. Funding provided by the U.S. Department of Homeland Security, Office of Domestic Preparedness.