In some extreme cases, thunderstorms can spawn a derecho, a long-lived windstorm with gusts over 100 mph, strong enough to cause widespread destruction. If a severe thunderstorm warning mentions damaging winds or a derecho, take cover immediately—just as you would for a tornado.

Unusually vicious and damaging weather across multiple U.S. states spawned violent tornadoes, blinding dust storms and fast-moving wildfires over the weekend, leaving at least 39 people dead. In the latest tally of the destruction,

Violent storms and tornadoes have been ravaging the U.S. for several days. At least 34 people have died, and dozens more have been injured. In Alabama, a tornado swept up a school bus, which crashed into a high school building,