All thunderstorms produce lightning and have the potential for danger. Those dangers can include tornadoes, strong wind, hail, wildfires, and flash flooding, which is responsible for more fatalities than any other thunderstorm-related hazard.
Lightning is most dangerous because of its unpredictability, which emphasizes the importance of preparedness. Lightning often strikes outside of heavy rain and can even occur as far as 10 miles away from rainfall. Most lightning-related deaths and injuries occur when people are caught outdoors in the summer months during the afternoon and evening. The Office of Emergency Management’s (OEM) thunderstorms flyer (pdf) can help you start preparing.
Differences between a warning and a watch
A severe thunderstorm is a thunderstorm with winds 58 mph or faster, or hailstones ¾ of an inch or larger in diameter.
Severe thunderstorm watch
A warning that thunderstorms might form, and could eventually produce wind gusts greater than 58 mph and/or hail greater than ¾ of an inch in diameter.
Severe thunderstorm warning
A warning that severe thunderstorms will occur.
Before a thunderstorm
- Remove dead or rotting trees and branches that could fall, cause injury, or damage to property.
- Postpone outdoor activities.
- Secure outdoor objects that could blow away or cause damage.
- Shutter windows and secure outside doors. If shutters are not available, close window blinds, shades, or curtains.
- Unplug appliances, televisions, computers, and air conditioners. Power surges from lightning can cause serious damage.
- Be sure to review the Severe Weather Safety Guide (pdf) for more information.
Remember, 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.
Remember the 30/30 lightning safety rule
After seeing lightning, if you cannot count to 30 before hearing thunder, go indoors. Stay indoors for 30 minutes after hearing the last clap of thunder
During a thunderstorm
- Stay inside a building or hard-top vehicle.
- Stay clear of tall, isolated trees, hilltops, open fields, beaches, or any metal object that may act as a lightning rod.
- Avoid showering, bathing, and using a phone that has a cord, except in an emergency. (Cordless and cellular phones are safe to use.)
- Take cover immediately if you are caught outside. Never stand under a tall tree or in an open area.
- Do not touch metal, electrical equipment, telephones, bathtubs, water faucets, or sinks.
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 valley. Be alert for flash floods.
In open water:
Get to land and find shelter immediately.
When you 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 to the ground. Do not lie flat on the ground.