Six people were killed in Illinois as twisters flattened entire blocks in some towns.
A violent storm that brought rare, late-season tornadoes to the Midwest was heading to the northeast and out to sea Monday, leaving behind death and destruction in 12 states, including some communities with entire blocks of houses flattened.
The death toll stood at seven with scores of injuries reported. Authorities feared the casualty list would climb as towns began to clear roads and restore communications.
The wave of thunderstorms Sunday brought damaging winds and tornadoes to Michigan, Wisconsin, Iowa, Illinois, Missouri, Indiana, Ohio, Kentucky, Tennessee, West Virginia, Pennsylvania and western New York.
Six deaths were reported in Illinois, one in Michigan.
Illinois Gov. Pat Quinn on Monday declared disaster emergencies in seven counties. He lauded first responders for "working to exhaustion" to search for survivors and clear roads. And he vowed to work with the federal and local governments to expedite recovery.
"We're in this together," Quinn said at a brief press conference. "We're a team. We are the people of Illinois -- we never give up, never surrender. We will prevail."
The National Weather Service said showers and thunderstorms would continue to develop as the storm moved eastward into New England and Canada, but that the widespread severe weather threat had diminished.
The NWS said around 80 tornadoes were reported as of Sunday night, but that the actual number will likely be in the 30 to 40 range because the same tornado often gets reported multiple times.
In Illinois, an elderly man and his sister were killed when a tornado hit their home in the rural southern Illinois community of New Minden, coroner Mark Styninger said. Three people perished in Massac County in the state's southern tip, and one person died in Washington, outside Peoria.
Washington, a town of 16,000 about 140 miles southwest of Chicago, appeared to have been the hardest hit. A violent twister cut a path about an eighth of a mile wide from one side of town to the other, State Trooper Dustin Pierce said.
The National Weather Service said two tornadoes were rated EF-4, the second-highest rating on the Fujita scale, based on damage. Winds reached at least 166 mph in New Minden, and the Washington twister had winds estimated at up to 190 mph, the weather service said.
As a powerful tornado bore down on their Illinois farmhouse in Washington, Curt Zehr's wife and adult son didn't have time to do anything but scramble down the stairs into their basement. When the twister passed, the spot where the home had stood was nothing but rubble.
Across farm fields a little more than a mile from where Zehr's home was swept up, several blocks of homes in one neighborhood were destroyed.
"The whole neighborhood's gone. The wall of my fireplace is all that is left of my house," said Michael Perdun, speaking by cellphone.
The Illinois National Guard said it had dispatched 10 firefighters and three vehicles to the town to help with search and recovery operations.
At OSF Saint Francis Medical Center in nearby Peoria, spokeswoman Amy Paul said 37 patients had been treated, eight with injuries ranging from broken bones to head injuries. Another hospital, Methodist Medical Center in Peoria, treated more than a dozen, but officials there said none of them were seriously injured.
In Lebanon, Ind., Melinda Wissig, a shift supervisor at Starbucks, said she looked up as someone shouted and saw a funnel bearing down on the coffee shop.
She rushed to the drive-thru to warn customers to come inside then took shelter with 10 other people in a bathroom, The Indianapolis Star reports. Wissig said she heard "a lot of crashing glass" Then, after two or three minutes, silence.
When she came out, Wissig saw a floor covered with debris, windows blown out and a car flipped upside down on to the sidewalk out from. But no one was injured.
In metro Detroit, power was knocked out for 459,000 people. In Indianapolis, an historic police office, built in 1903 in the neighborhood of Irvington, was demolished by strong winds and heavy rain.
As high winds slammed into the Chicago area, officials at Soldier Field evacuated the stands and ordered the Bears and Ravens off the field. Fans were allowed back to their seats shortly after 2 p.m., and the game resumed after about a two-hour delay.
Weather service meteorologist Matt Friedlein said such strong storms are rare this late in the year because there usually isn't enough heat from the sun to sustain the thunderstorms.
But he said temperatures Sunday had been expected to reach into the 60s and 70s, which he said is warm enough to help produce severe weather when it is coupled with winds, which are typically stronger this time of year than in the summer.
"You don't need temperatures in the 80s and 90s to produce severe weather (because) the strong winds compensate for for the lack of heating," Friedlein said. "That sets the stage for what we call wind shear, which may produce tornadoes."
Contributing: John Bacon in McLean, Va.; Alex Campbell, reporter for The Indianapolis Star, in Lebanon, Ind.; Associated Press