All thunderstorms are dangerous despite the fact that they are generally localized in a small geographical region. It is important to note that every thunderstorm produces lightning, which is responsible for more deaths annually than hurricanes or tornadoes.
The National Weather Service classifies a thunderstorm as severe if it has wind gusts greater than 58 mph, hail that is 3/4 inch in diameter or produces a toronado. Severe thunderstorms can lead to flash flooding, straight-line winds of 100 to 150 mph, damaging hail and tornadoes. A typical thunderstorm is 15 miles in diameter and lasts for 20-30 minutes. On average, 100,000 thunderstorms occur in the United States each year with 10% (10,000) classified as severe.
Terms to know:
Severe storm WATCH means that severe storms are possible and it is important to pay attention to weather reports and be ready to find shelter if a warning is issued.
Severe storm WARNING indicates that severe weather has been reported by spotters and there is imminent danger to life and property. Take cover immediately.
Severe storm preparedness guide - National Weather Service and American Red Cross.
Severe weather planning guide for schools - National Oceanic and Atmospheric Administration (NOAA).
Nationwide severe weather maps - University of Kentucky. State maps are easily accessible through efforts of Tom Priddy.
Lightning is a major threat during a thunderstorm because it is very unpredictable and it can strike as far as 10 miles away from the actual rainfall area. An average of 62 people are killed from lightning strikes each year with the majority of deaths occurring to people who did not seek inside shelter during the storm. Many more injuries occur and some may result in long-term, debilitating symptoms such as memory loss, sleep disorders, attention deficits, irritability, depression and muscle spasms.
Do you know the 30/30 rule for lightning safety?
First 30: if there are 30 seconds or less between the lightning flash and hearing thunder, then the lightning is close enough to strike you -- go inside immediately. Second 30: wait 30 minutes after the last lightning flash before leaving your inside shelter area.
Lightning safety website - NOAA
Lightning Safety on the Job - NOAA
Coaches and Sports Officials Guide to Lightning Safety - NOAA
Safety Tips for the Mariner - NOAA