According to the Weather Channel, the worst thunderstorm in the U.S. in terms of cost took place on May 5, 1995 in Fort Worth, Texas. Hail damage alone was over $2 billion, not counting wind or rain damages. Prior to this, only hurricanes had damage figures in the billions.
The thunderstorm struck during the outdoor Mayfest festival near downtown Fort Worth, which increased the damage because many victims were caught outdoors with no access to shelter. Festival attendees were subject to 70-mph winds and hail the size of grapefruits. The aftermath of the storm looked like winter in Texas, with bare trees and ice coating the ground.