Thunderstorms occur most often throughout the western and southeastern United States and along the Gulf Coast. They can form all throughout the year and at any hour during the day, but are more common during the summer and spring. The majority of thunderstorms in the Plains states develop during the afternoon, but regularly occur late in the afternoon and during nighttime hours.
Thunderstorms are rain showers that result in thunder and may be classified as a "severe" thunderstorms if winds above 50 knots, tornadoes or hailstones greater than 1 inch are detected. The U.S. experiences about 100,000 thunderstorms each year, with only around 10 percent being classified as "severe."