The U.S. National Weather Service defines a severe thunderstorm as any one of the following: a thunderstorm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least 1″ (2.5 cm) in diameter. #SevereWxAwarenessWeekpic.twitter.com/lXjPqZ6Ql7

The U.S. National Weather Service defines a severe thunderstorm as any one of the following: a thunderstorm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least 1″ (2.5 cm) in diameter. 

Source: Twitter NWS Burlington