Violent tornadoes ripped through parts of the U.S., wiping out schools and toppling semitractor-trailers in several states.

Millions of Americans across the country are on alert for a severe weather outbreak as violent, long-track tornadoes with damaging winds of up to 80 mph and large hail are expected across the Midwest and South with the cross-country storm moveing east.

At least 16 people have died as severe storms have hit the South and Midwest regions of the United States on Saturday (March 15), NBC News reports. An estimated 138 million Americans are reportedly at risk of severe weather as tornado warnings have already been issued in Illinois,