The peak season for severe weather in the United States typically falls between March and October, but severe weather can happen at any time.
Knowing the difference between Watches and Warnings is essential to help you plan on how to handle severe weather occurrences.
Watches are issued by the NOAA’s Storm Prediction Center, or SPC. If conditions are favorable for a severe thunderstorm or tornado, then a watch will be issued.
Watches do not mean that severe weather will happen – it just means the conditions for severe weather are right. The likelihood is greatly increased.
According to the SPC, a typical watch will cover about 25,000 square miles – about half the size of Iowa. There is no set criteria for issuing a watch. Scientists just look for conditions to be consistent with severe weather to develop.
Warnings are issued by local National Weather Services offices. Severe weather is imminent, and, unlike watches, warnings have specific criteria that must be met before they are issued.
Hail that totals more than an inch in diameter or wind speeds of 55 miles per hour or faster triggers a warning event. Lightning and heavy rain are not factors for severe thunderstorm or tornado warnings. Urban flood, stream advisories, flash flood watches and warnings and flood watches and warnings may accompany a storm with heavy rain.
Meteorologists will monitor the weather and issue warnings that are verified by trained NWS spotters.
Since warnings are issued by local NWS offices, they are generally more regionally specific.