A deep freeze set in across the Midwest on Sunday with low temperatures forecast in the single digits and a few below zero, turning the season's first major snow into ice that made some roads treacherous to travel.

Temperatures plunged behind a cold front that brought snow across much of the region Friday and Saturday.

The National Weather Service forecast 20 degrees or lower across six states from North Dakota to Illinois. The weather service reported temperatures in the single- and low double-digits Sunday in northern Illinois, including Chicago, where residents were digging out of more than 11 inches of snow -- the highest November total in 120 years in the city.

More than 130 flights were cancelled Sunday into and out of the O'Hare International Airport in Chicago, according to flight-tracking website FlightAware.com.

In Minneapolis, dozens of people huddled around fires to stay warm at an encampment outside a police station to protest the fatal shooting of a black man by officers there last week. Temperatures hit a low of 17 degrees overnight, and light snow was expected by Sunday evening.