What's the difference between a watch and a warning?

July 11, 2008 7:06:15 AM PDT
A Severe Thunderstorm Watch means that atmospheric conditions are favorable for severe thunderstorms. Severe thunderstorms contain hail at least penny-sized, and/or winds in excess of 58 mph.

Erica's Answer:

A Severe Thunderstorm Warning means that these conditions are already occurring in that location.

The same rules apply for Tornado Watches and Warnings. A Tornado Watch means conditions are favorable for tornadic development, whereas a Tornado Warning means that a tornado has been spotted, either by a trained spotter on the ground or by Doppler radar.

- Erica