A thunderstorm is considered severe if it produces hail at least 1 inch in diameter or has wind gusts of at least 58 miles per hour. Every thunderstorm produces lightning, which kills more people each year than tornadoes or hurricanes. Heavy rain from thunderstorms can cause flash flooding and high winds can damage homes and blow down trees and utility poles, causing widespread power outages.

Know the difference between a severe thunderstorm WATCH and a thunderstorm WARNING.

Severe Thunderstorm Watch—Severe thunderstorms are possible in and near the watch area. Stay informed and be ready to act if a severe thunderstorm warning is issued.

Severe Thunderstorm Warning—Severe weather has been reported by spotters or indicated by radar. Warnings indicate imminent danger to life and property.

Click here to learn what to do BEFORE a thunderstorm.

Click here to learn what to do DURING a thunderstorm.

Click here to learn what to do AFTER a thunderstorm.

Every year people are killed or seriously injured by severe thunderstorms despite advance warning. While some did not hear the warning, others heard the warning and did not pay attention to it. The information in this section, combined with timely watches and warnings about severe weather, may help save lives.

Click here for the Thunderstorm Safety Checklist.