Lightning is so dangerous that it claims an average of 93 lives each year in the United States. Another 300 people are inflicted with injuries each year due to lightning strikes. Most flash flood deaths occur at night and when people become trapped in automobiles. Several factors contribute to flash flooding. The two key elements are rainfall intensity and duration.
Intensity is the rate of rainfall and duration is how long the rain lasts.
Topography, soil conditions, and ground cover also play an important role. Turn around and go another way. Although they are found in many parts of the world, tornadoes are most common in the United States east of the Rocky Mountains during the spring and summer months. Tornadoes are defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent of tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more.