What does it mean if a thunderstorm watch is issued?

A severe thunderstorm watch means that general conditions in a region favor the formation of severe thunderstorms. It does not indicate any immediate threat. When a storm becomes severe or threatens to become so, a severe thunderstorm warning is issued.

Severe thunderstorms carry the risk for wind gusts to 58 mph or greater, hail 1" or larger in diameter, and tornadoes. Note, though, that if conditions are favorable for thunderstorms to produce tornadoes, a tornado watch is issued instead.