The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Despite their small size, thunderstorms are dangerous. Every thunderstorm produces lightning which kills more people each year than tornadoes. Heavy rain from thunderstorms can lead to flash flooding. Strong winds, hail, and tornadoes are also dangers associated with some thunderstorms.
Lightning occurs with all thunderstorms.
It averages 93 deaths and 300 injuries each year. It also causes several hundred million dollars in damage to property and forests annually. Most flash flood deaths occur at night and when people become trapped in automobiles. Straight line winds are responsible for most thunderstorm wind damage. One type of straight line wind that can cause extreme damage is a downburst , a small area of rapidly descending air beneath a thunderstorm.