"Occasionally we have a death but we have warning system. Seven deaths. It's been a long time since we've had those kinds of injuries and deaths reported," Miller said.
Witnesses reported parts of Parkersburg — particularly the town's south side — were reduced to rubble, including most of the town's high school and homes. In the Des Moines area, there was heavy rain and lightning Sunday night with wind gusts of 70 mph.
Iowa Gov. Chet Culver issued a disaster proclamation for Black Hawk, Buchanan and Butler counties, a move that helps coordination between state and local authorities.
The storms came after three days of violent weather across the nation. Rural Oklahoma was battered Saturday and storms in Kansas a day earlier killed at least two people there.
Tim Halback, of the National Weather Service, in Romeoville, Ill., said the storms are the result of a massive warm system that had been centered over the southern and western great Plains several days ago. When it began moving northward into Minnesota and Canada, a cold high followed in its wake, sparking severe storms.
The hazy weather now stretches from northwestern Minnesota and western Iowa into western Kansas, and was expected to move eastward across Wisconsin, Illinois and Indiana later Monday.
Severe thunderstorm warnings were issued early Monday for Cook County in northeast Minnesota, and three counties in Missouri: Osage, Gasconade and Montgomery.
At least 20 people were unaccounted for Sunday in Minnesota after a swift storm blew through the St. Paul suburb of Hugo, damaging about four dozen homes, City Administrator Mike Ericson said.
A 2-year-old child was killed and the child's sibling was critically injured, Washington County Sheriff Bill Hutton said. The children's parents also were hospitalized with injuries sustained in the family home.
"It's horrible," Ericson said. "The citizens are very shook and scared." Gov. Tim Pawlenty announced plans to meet with city officials and tour the storm-ravaged city on Monday.
Roughly 300 to 400 homes were evacuated in the storm-damaged area because of concerns over hazards including downed power lines and leaky gas lines, Ericson said.
The city set up a shelter at an elementary school, but American Red Cross spokeswoman Courtney Johnson said all but one of the families was able to find a place to stay with friends or relatives.
Hugo Public Works Director Chris Petree said his family took shelter in the basement before the storm lifted his house off the ground and completely wiped out the second floor.
"I put my daughter down first, my wife on top of her and then I bear-hugged on top of them," Petree said.
As he huddled in his basement against a foundation wall with his wife and 2½-year-old daughter, Petree said they heard the thunderous sound of their house coming off the ground.
"All you hear is glass breaking and wood tearing and breaking in half," Petree said.
The National Weather Service issued a tornado watch about 6 p.m. for 45 of Wisconsin's 72 counties, but canceled the alert five hours later as the storms began to ease. At least 16,000 people across Wisconsin lost power at some point.
At least three weak tornadoes touched down in the Texas Panhandle. There were no reports of injuries or building damage across the sparsely populated region, meteorologist Jason Jordan said.
About 100 people have died in U.S. twisters so far this year, the worst toll in a decade, according to the weather service, and the danger has not passed yet. Tornado season typically peaks in the spring and early summer, then again in the late fall.