Tornadoes get a lot of the attention, but flash flooding can be even more dangerous. In the United States, flooding kills an average of nearly 100 people each year, compared to about 90 for tornadoes.

It doesn't take much to be dangerous, either. 6 inches of moving water can knock you off your feet, and 2 feet of moving water can sweep away most vehicles. Even if the floodwater isn't moving, it's still a hazard–it may have chemicals or manure in it.