The Midwestern US is being battered by heavy rain and strong winds by a storm some forecasters are comparing to a category three hurricane.
Forecasters told residents of the state of Illinois to expect the most powerful storm to hit the region in over 70 years.
Tornado warnings were issued across the US from the state of Arkansas to Illinois's metropolitan hub of Chicago.
The storm delayed flights at the city's O'Hare International Airport.
Severe thunderstorm warnings have been announced across the Midwestern US, as the storm continues to charge through the country - moving from North and South Dakota to the eastern Great Lakes, on the border with Canada.
The storm is carrying with it pressure levels similar to a category three hurricane, meteorologist Amy Seeley said.
Although the effects of the storm will not be the same as those for a hurricane, wind gusts are predicted to be as strong as those experienced in a tropical storm.
Sustained winds of 35-40mph (56-64km/h) and gusts up to 60mph were expected throughout the afternoon, the National Weather Service said.
The winds blew off rooftops at a factory in the town of Mount Pleasant in Wisconsin and a home in Peotone in Illinois.
"This is a very different type of event," said meteorologist Edward Fenelon.
"But that does give an indication of the magnitude of the winds. This isn't something you see even every year."
Morning commuters in Chicago faced blustery rain that flipped umbrellas inside out and snapped some of them in half.
"The wind was almost blowing horizontally. The rain was slapping me in the face. My umbrella shot off. It was pretty dangerous," Chicago resident Anthony Kwit told the Associated Press news agency.
He added that his car "was starting to veer off the road" as the result of strong winds.
Twitter users have nicknamed the storm "chiclone" and "windpocalypse".
The energy company ComEd was already trying to restore power to roughly 5,600 customers in Illinois early on Tuesday, spokesman Bennie Currie said.