Glossary
Flash flood
Flooding that starts within about 6 hours of heavy rain, often faster. It can happen on city streets and underpasses.
A flash flood is flooding that begins quickly, within 6 hours and often within 3 hours of heavy rain, according to the National Weather Service (opens in a new tab). It can happen anywhere: quiet streams can become torrents, and city streets and highway underpasses can flood fast.
Floodwater is a drowning hazard. The NWS (opens in a new tab) says more deaths occur from flooding each year than from any other thunderstorm-related hazard, and that over half of flood-related drownings happen when a vehicle is driven into hazardous flood water; the next largest share happens to people walking into or near floodwater. Its warnings:
- just 6 inches of fast-moving water can knock over an adult;
- 12 inches of rushing water can carry away most cars, and 2 feet can carry away SUVs and trucks;
- never drive around barriers on a flooded road, because the road beneath may have collapsed.
The CDC (opens in a new tab) also says to check the forecast before activities near water, since weather can change quickly and cause flash floods. See flash flood safety at home and Turn Around Don't Drown.
What you can do today: sign up for local emergency alerts on your phone.