Severe thunderstorms sweeping through the Midwest have killed a motorist in Michigan, shattered windows in an iconic Chicago skyscraper and knocked out power to hundreds of thousands of people.

Sheriff's officials say a driver was killed near Dexter, Mich., about 40 miles west of Detroit, when winds toppled a tree onto a vehicle.

In Chicago, powerful winds and heavy rains broke windows in the 110-story Willis Tower. Utility officials say power is out for about 280,300 Chicago-area customers and 150,000 in Michigan.

Earlier this week, a series of tornadoes ripped across Minnesota, leaving two people dead and injuring dozens more.

One twister in southern Minnesota turned the late afternoon sky to black and, at times, was as big as half a mile wide.

The storms flattened homes, uprooted trees, and downed power lines.

"They say it sounds like a freight train. It does," said 38-year-old Jay Hotakainen, who had huddled in his basement with his 12-year-old son, Lee, and 6-year-old daughter Emma.

Some of the hardest hit areas were in the northwest part of the state.

An elderly woman was killed when a tornado destroyed her home, and a man died when a twister hit a gas station.

Gov. Tim Pawlenty planned to visit the damaged region later Friday.  "Our emergency management officials have been working closely with local officials and we stand ready to assist in every way needed," the governor said in a statement. "Tomorrow we will visit the areas hit hardest by these tornadoes to ensure that the response is swift and comprehensive."