At least 34 people have died in the US after violent tornadoes tore through several south-eastern states, flipping cars and flattening homes. In Kansas, a dust storm on Friday afternoon caused a crash with more than 50 vehicles, killing at least 8 people. Texas saw a similar mass pile-up.

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.