How does the National Weather Service (NWS) define a severe thunderstorm?
The term severe thunderstorm refers to a thunderstorm producing hail that is at least penny size, 0.75 inches in diameter or larger, and/or wind gusts to 58 mph or greater, and/or a tornado. Although lightning can be deadly, the NWS doesn’t use it to define a severe thunderstorm. If it did, every thnderstorm would be severe, by definition. Also, excessive rainfall may lead to deadly flash flooding, but heavy rain is not a severe criterion either. The flood threat is handled through a separate set of watches and warnings from your lcoal NWS forecast office.
