Mark Styninger, the coroner of Washington County in southern Illinois, said an elderly man and his sister were killed around noon CT when a tornado hit their home in the rural community of New Minden.
MORE: Frightening images from Soldier Field as storm hits
In central Illinois, the town of Washington appeared particularly hard-hit, with one resident saying his neighborhood was wiped out in a matter of seconds by a tornado.
"I stepped outside and I heard it coming. My daughter was already in the basement, so I ran downstairs and grabbed her, crouched in the laundry room and all of a sudden I could see daylight up the stairway and my house was gone," Michael Perdun said Sunday afternoon in an interview with The Associated Press on his cellphone. "The whole neighborhood's gone, (and) the wall of my fireplace is all that is left of my house."
By mid-afternoon it remained unclear how many people were injured. In a news release, the Illinois National Guard said it had dispatched 10 firefighters and three vehicles to Washington to assist with "immediate search and recovery operations in the tornado damaged area."
And Steve Brewer, chief operating officer at Methodist Medical Center of Illinois in Peoria, said that four or five people had come to the hospital seeking treatment, but he described their injuries as minor. He said another area hospital had received about 15 patients, but did not know the severity of their injuries.
Brewer said doctors and other medical professionals were setting up a temporary emergency care center to treat the injured before transporting them to area hospitals.
"I went over there immediately after the tornado, walking through the neighborhoods, and I couldn't even tell what street I was on," Alderman Tyler Gee told WLS-TV. "Just completely flattened — some of the neighborhoods here in town, hundreds of homes."
About 90 minutes after the tornado destroyed homes in Washington, the storm darkened downtown Chicago. As the rain and high winds slammed into the area, officials at Soldier Field evacuated the stands and ordered the Bears and Baltimore 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.
Earlier, the Office of Emergency Management and Communications issued a warning to fans, urging them "to take extra precautions and ... appropriate measures to ensure their personal safety." NFL games in Cincinnati and Pittsburgh also could be affected by the rough weather.
Just how many tornadoes hit was unclear Sunday afternoon. According to the National Weather Services' website, a total of 59 tornadoes had struck, the bulk of them in Illinois. But meteorologist Matt Friedlein said the total might fall because emergency workers, tornado spotters and others often report the same tornado.
Still, when the weather service was issuing its warning that severe weather was bearing down on the Midwest, officials said the last such warning issued in November came in 2005, and the result was an outbreak of 49 tornadoes.
The storm also followed dire warnings by the weather service that the storm was simply moving too fast for people to wait until they saw it to get ready.
"Our primary message is this is a dangerous weather system that has the potential to be extremely deadly and destructive," said Laura Furgione, deputy director of the National Weather Service National Oceanic and Atmospheric Administration. "Get ready now."
In fact, the weather service said officials confirmed that a tornado touched down just before 11 a.m. near the central Illinois community of East Peoria, about 150 miles southwest of Chicago, but authorities did not immediately have damage or injury reports. Within an hour, the weather service said that tornadoes had touched down in Washington, Metamora, Morton and other central Illinois communities, though officials could not say whether it was one tornado touching down or several.
"This is a very dangerous situation," said Russell Schneider, director of the weather service's Storm Prediction Center. "Approximately 53 million in 10 states are at significant risk for thunderstorms and tornadoes."
The potential severity of the storm this late in the season also carries the risk of surprise.
"People can fall into complacency because they don't see severe weather and tornadoes, but we do stress that they should keep a vigilant eye on the weather and have a means to hear a tornado warning because things can change very quickly," said Matt Friedlein, a weather service meteorologist.
According to agency officials, parts of Illinois, Indiana, southern Michigan and western Ohio were at the greatest risk of seeing tornadoes, large hail and damaging winds throughout the day Sunday. Strong winds and atmospheric instability were expected to sweep across the central Plains during the day before pushing into the mid-Atlantic states and northeast by evening. Many of the storms were expected to become supercells, with the potential to produce tornadoes, large hail and destructive winds.
Friedlein said that 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 were 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 the lack of heating," he said. "That sets the stage for what we call wind shear, which may produce tornadoes."
He also said that the tornadoes this time a year happen more often than people might realize, pointing to a twister that hit the Rockford, Ill., area in November 2010.
