The worst overall problems were at Chicago O'Hare, where more than 1,200 flights had been canceled as of noon ET, according to flight-tracking service FlightAware.
Southwest Airlines has canceled most flights tonight and Sunday, according to Midway Airport officials.
Ninety-eight flights were canceled at O'Hare and 63 at Midway as of 10 p.m., according to real-time flight statistics provided by the Chicago Department of Aviation.
The wintry weather mostly moved out of the Plains overnight, leaving parts of Minnesota with up to a foot of snow, and pushed into Wisconsin, Illinois, and Indiana. Consequently, hundreds of flights into and out of Chicago's Midway and O'Hare airports were grounded.
A winter-weather advisory was in effect for Sunday night into Monday in parts of Montana, with forecasts of up to a foot of snow in the mountains. By 6:30 p.m., almost 7 inches of snow was recorded at O'Hare International Airport. In Kirtland, Ohio, east of Cleveland, almost 33 inches of snow had fallen as of Saturday morning.
Up to 11 inches of snow were expected in some areas of Detroit, the Detroit Free Press reported. Both airports reported about seven inches of snow.
In Detroit, local media reports said no one was injured when an arriving Delta Air Lines slid into the grass around noon ET there.
Winter Storm Caly began in the Pacific Northwest late last week.
Temperatures 15 to 30 degrees below average will follow the cold rain and snow in the coming days through much of the Midwest and East.