Thunderstorms are dangerous because they bring the dangers of lightning, high winds, floods, and flash floods, from extremely heavy rainfall. By definition, a thunderstorm is a cloud that contains lightning and thunder. A typical storm is usually 15 miles in diameter lasting an average of 30 minutes. Every thunderstorm produces lightning, which kills more people each year than tornadoes.
Lightning often strikes outside of heavy rainfall and may occur as far as 10 miles from the rain. If you are outside during a lightning storm, seek inside shelter immediately and stay off the telephone. Debunking a myth, rubber-soled shoes and/or rubber tires privide NO protection from lightning. However, if lightning hits the car you are inside, the steel frame of a hard topped vehicle will provide increased protection provided you are not touching metal when your car is hit by lightning.
A severe thunderstorm is a thunderstorm that contains large hail (3/4 inch in diameter or larger), damaging or straight-line winds (58 mph or greater) and/or a tornado. A down burst is a strong out rush of wind formed by rain cooled air. Strong down bursts which produce extensive damage are often mistaken for tornados. A down burst can easily overturn a mobile home, tear roofs off houses and topple trees.
The National Weather Service considers a thunderstorm severe if it produces hail at least 3/4 inches in diameter, winds of at least 58 mph and/or a down burst.
Heavy rain from thunderstorms can lead to flash flooding. The power of flowing water can easily sweep away trees, buildings, automobiles and people. Missourians needlessly die when they drive theirs cars into low water crossings and drown when the car is swept off the road.
On an average, it takes about two feet of water for a car to float downstream. However, it takes less than one foot of water for a smaller car to stall. Once a car stalls, the driver normally gets out to wlat to safety. If the driver is not careful, he could be swept into deeper water beneath the low water crossing.
NEVER drive into a flooded area. NEVER drive around road barricades. NEVER assume the water isn't deep. Looks can be deceiving. How many times have television crews captured dramatic footage of rescue workers plucking victims out of flooded water downstream from low water crossings. While the water may only look two feet deep, it might be closer to five or six feet deep.
Be proactive. If you are camping near a small stream, be prepared to move quickly if flooding occurs. Heavy rain upstream may lead to serious flooding near your campsite with little or no warning. Avoid camping near streams if rain is forecast.