Thunderstorms with damaging winds or hail. The NWS defines a severe storm as one having winds greater than 57 mph or hail 3/4 inch in diameter or larger (dime size or bigger).
A thunderstorm producing damaging winds (trees down, etc.) or winds 58 mph or more and/or hail three-quarter of an inch or greater in diameter.
A thunderstorm that produces either of the following: damaging winds of 58 miles an hour or greater, hail 3/4 of an inch in diameter or larger, or a tornado. Severe thunderstorms can result in the loss of life and property.