A Severe Weather Watch is a National Weather Service product that identifies a broad region where severe thunderstorms or tornadoes are possible within a defined time window, typically the next four to eight hours. It is issued by NOAA's Storm Prediction Center in coordination with the local Weather Forecast Offices whose county warning areas it covers.
The two watch types
A Severe Thunderstorm Watch is issued when the environment favors thunderstorms that will meet severe criteria: hail of at least 1 inch in diameter or wind gusts of at least 58 mph. A Tornado Watch is issued when, in addition to severe thunderstorm potential, forecasters believe there is meaningful potential for tornadoes.
SPC can also apply a Particularly Dangerous Situation label to either watch type when the setup supports a heightened level of severe weather, such as strong or violent tornadoes, very large hail, or a widespread damaging wind event.
How watches are used
A watch is a decision trigger. Emergency managers move to higher readiness. Broadcasters interrupt regular programming more frequently. NWS forecast offices staff up for a warning shift. Members of the public in the watch area should review their shelter plan and monitor for warnings.
Watches are broad by design. A tornado watch often covers multiple counties across more than one state, because the environment that supports severe convection typically extends over that scale. The watch does not mean storms are guaranteed everywhere inside its footprint, only that the potential is real and the operational posture should reflect it.
Common misunderstandings
A watch is not a warning. It describes what the environment could support, not what a specific storm is doing. Some watches expire with only marginal weather. Others are followed by dozens of warnings inside the footprint. Both outcomes are consistent with the product doing its job.
A watch is also not a fence. Storms occasionally fire just outside the watch box, especially as the environment evolves late in the day. If a warning is issued in your area, respond to the warning regardless of whether the point you are standing on is inside the watch polygon.