Thunderstorms affect relatively small areas when compared to hurricanes and winter storms. The typical Thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Nearly 1,800 thunderstorms are occurring at any moment around the world. That's 16 million storms a year! Despite their small size, all thunderstorms are dangerous. Every thunderstorm produces lightning, which kills more people each year than tornadoes. Heavy rains from thunderstorms can lead to flash flooding. Strong winds, hail, and tornadoes are also dangers associated with some storms.