Rebecca asked what conditions make a storm become severe. There are three criteria the National Weather Service look at to determine if a storm is severe.
The first is hail size. When a storm is producing hail larger than an inch in diameter, the storm becomes severe.
The second is wind speed. A storm is severe when wind gusts exceed 58 miles per hour, which is enough to uproot trees and cause damage to structures.
The last factor that will make a storm severe is if it contains a tornado.
A storm only needs to meet one of these criteria to be classified as a severe storm.
According to the National Severe Storms Laboratory, there are around 100,000 thundestorms in the U.S. every year. Only around 10% of those storms become severe.
Hail causes around $1 billion in damage to crops and property every year in the U.S., while tornadoes cause around $400 million in damage per year in the u.S.