Monday is probably the peak of this event, but a concerning storm risk shifts eastward Tuesday. Cities in the highest risk for tornadoes include Minneapolis and Rochester in Minnesota and La Crosse in Wisconsin.

Millions in the Upper Midwest face the possibility of a severe thunderstorm outbreak Monday—the start of several days of extreme weather threats across the country this week.

More than 36 million Americans are on alert for severe weather in the Upper Midwest, with thunderstorms, large hail and a tornado outbreak possible starting Monday.

A potentially life-threatening severe weather outbreak is likely across the Upper Midwest on Monday as tens of millions of people prepare for powerful thunderstorms capable of producing very large hail,