A massive storm system that brought tornadoes, rain, high winds and wildfires killed dozens of people in the Midwest and South over the weekend.

At least 30 people died as violent weather swept the country on Friday and Saturday, and the threat isn't over.

Communities across Missouri, Illinois, and Indiana were devastated by the deadliest and longest-running tornado ever recorded a century ago. Here's what happened.

Tornadoes whipped through Missouri on Friday night, ripping apart homes, businesses, and the electrical system. Gov. Mike Kehoe’s Office says at least 12 people have been killed and one person is still missing from the severe weather.

The deadliest twister in recorded U.S. history struck 100 years ago Tuesday, touching down in southeastern Missouri and tearing up everything in its 219-mile (352-kilometer) path for nearly four hours through southern Illinois and into Indiana.

"The scale of devastation across our state is staggering," Missouri Gov. Mike Kehoe said. "While we grieve the lives of those lost, we are also focused on action."

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.

"Get to the sturdiest structure you have access to and remain in place until the storms pass," the NWS told residents in Alabama on Saturday night, when multiple tornado warnings were issued. At least 250,