More tornadoes touched down late Monday in Oklahoma, Nebraska, Missouri and Kansas.
Four were reported in or near Chillicothe, Mo., where a hospital said it treated 10 people for minor injuries. Two girls injured were in a trailer home that was picked up by a tornado and dropped onto a car.
A tornado even touched down in eastern New York, destroying a camper and barn in a sparsely populated area about 75 miles southeast of Syracuse.
In Hallam, Nebraska - where a Saturday twister a mile and a half wide flattened nearly every house in town - police Monday began allowing residents and repair workers back into town.
"It's tough to come and see your house with a condemned sign on it," resident Lisa Chelton told CBS News.
Hours later, they had to order everyone out again - as a precaution against threatening weather that appeared to be setting up for yet another tornado.
Several more tornadoes were reported Monday southwest of Hallam in Nuckolls and Thayer counties, including one that took the roof off of a house, destroyed several grain bins and downed power lines, said Steve Carmel, a meteorologist at the National Weather Service in Hastings. Officials are continuing to tally up the damage.
Saturday's twisters killed a 73-year-old Hallam woman, injured 37 other people, destroyed 158 homes and damaged at least 57 others in Lancaster, Saline, Gage and Cass counties.
"It's just about a total loss," said Millie Schuster, whose possessions were reduced to an heirloom clock, the family Bible and a closet full of clothes.
Another Hallam resident couldn't help thinking of the dreams she had when she first moved into the house that is now only a memory.
"We found a house we loved," said Marcene Pullman. "It's gone now."
Piles of corn and milo, a type of livestock feed, covered the streets of Hallam, a village of 276 where earlier Monday the sounds of chain saws, electric generators and heavy equipment filled the air.
"I don't think there's a habitable structure - maybe one house," said Chief Deputy Sheriff Bill Jarrett of Lancaster County.
Dick Hainje, regional director of the Federal Emergency Management Agency, flew over tornado-ravaged villages with Nebraska Gov. Mike Johanns and Sen. Chuck Hagel. Johanns has requested a presidential disaster declaration for 10 Nebraska counties.
A tornado touched down briefly in the western Oklahoma town of Alfalfa Monday evening, destroying a fire station, and damaging several homes and a mechanic's shop, authorities said.
"They had roof damage, windows broken out of residences, outbuildings totally destroyed, trees uprooted," said Caddo County Sheriff's dispatcher Mary Duree. She said there were no injuries.
In the northern Illinois community of Gurnee, residents Monday battled the rising waters of the Des Plaines River in what threatened to become the town's worst flood in two decades.
"I can't stop the water," said Sandy Snell, one of the many watching the water rise in Gurnee, where it is expected to break a high water mark set in 1986. "All I can do is pray that everything is okay."
The floodwaters forced schools to close for more than 2,000 youngsters, and homes and businesses filled with water, including the Gurnee Community Church. Pumps belched water out a church window, a sign overhead reading, "We've got peace like a river."
"Spirits here are high. We're all helping each other out," said resident John Goodwin, 45.
The river in Gurnee is expected to crest early Wednesday at 12.7 feet - 5.7 feet over flood level.
Further south in the Chicago suburb of Des Plaines, authorities were distributing sandbags and preparing fliers alerting residents of the rising water levels, said Dave Niemeyer, Des Plaines' city manager.
The river is expected to crest at 11.2 feet in Des Plaines early Thursday, a record-setting 6.2 feet over the flood stage, the National Weather Service said.
Flooding is also a problem in Iowa, where storms beginning Friday produced a string of 19 tornadoes, hail, high winds and heavy rains. As much as 9 inches fell over the weekend near Ames.
Iowa Gov. Tom Vilsack asked for a federal disaster declaration covering 23 counties.
Near the overflowing Malone Creek in the eastern Iowa town of Independence, townspeople were cheered by news the river was receding - even as they braced for more storms.
"The ground all around the county is saturated and just can't take any more water," said Ed Fitzgerald, spokesman for Buchanan County, Iowa, Emergency Management.
Several thousand Ohioans remained without power Monday following weekend thunderstorms, and more storms caused new outages. Several schools in central Ohio were closed because they lacked electricity.
More than 20 counties in southeastern and east-central sections of Lower Michigan are under flood warnings. The storms that began Friday knocked out power to at least 540,000 Michigan homes and businesses, as many as 38,600 of which remained without power Monday night.
In Rochester, N.Y., lightning ignited a natural gas line, shooting flames 20 feet into the air, and thousands of homes had no electricity after thunderstorms laid a trail of damage across upstate New York.