The U.S. WeatherBureau started reporting tornadoes, thunderstorms, hailstorms, lightning and high winds at a few experimental locations across the United States in spring 1943.
In 1953, the U.S. WeatherBureau established the Severe Local Storms Center, known as SELS. The first tornado watches issued by SELS usually covered an average area of 27, 000 square miles.