More than 200,000 homes and businesses in the US have been without power after storms with damaging winds, lightning and baseball-sized hail struck parts of the Dakotas, Minnesota, and Wisconsin.
A 63-year-old woman sheltering in a bathtub also died after powerful winds tossed her around her trailer in South Dakota.
Storms developed in the Dakotas on Friday and drove through Minnesota into Wisconsin, producing wind gusts of up to 137kph and large hailstones, some in excess of 10cm in diameter, as well as short-lived tornadoes.
"Some 200,000 customers were still without power in Minnesota on Saturday, mainly in the Minneapolis area, and another 1,000 were without power across the border in Wisconsin," said Tom Hoen, a spokesman for Xcel Energy, which serves the area.
Hoen said there would be customers without service going into Tuesday because of the massive scale of the damage.
He added that the outages had affected 492,000 customers since the storm formed.
Other utility companies reported scattered outages in Minnesota and Wisconsin.