Quinn declared seven counties a state disaster area, including Tazewell County, just east of Peoria in central Illinois, where a tornado left parts of Washington in ruins and one person dead.
"Devastation. Sadness. People that lost everything," is how Washington Mayor Gary Manier described the scene to CNN's Chris Cuomo on "New Day."
Another tornado in Washington County, Illinois, east of St. Louis, left a path of debris that stretched more than three miles, according to a preliminary survey by the National Weather Service.
While the bulk of the storm system had moved offshore into the Atlantic Ocean and the threat of severe weather Monday was small, damaging wind gusts of up to 40 mph were still possible in parts of the Northeast, CNN meteorologist Indra Petersons said Monday morning. In the Great Lakes region, 50 mph gusts were possible, she said.
Hundreds of thousands of people remained without power.