In Chicago, temperatures were expected to bottom out around minus 15 F (minus 26 C) overnight, likely setting a daily record, National Weather Service meteorologist Ed Fenelon said.
Earlier Sunday, temperatures sank to 20-below F (29-below C) and colder in northern Minnesota and Grand Forks, North Dakota.
The deep freeze extended into Canada where parts of eastern Alberta and northwest Ontario were under wind chill warnings. In Winnipeg, Manitoba, temperatures fell to minus 22 F (minus 30 C) on Sunday.
It hasn't been this cold for almost two decades in many parts of the US. Frostbite and hypothermia can set in quickly at 15 to 30 below zero F (26 to 34.4 below zero C).
Travel problems started early Sunday. In New York City, a plane from Toronto landed at Kennedy International Airport and then slid into snow on a taxiway. No one was hurt, though the airport temporarily suspended operations because of icy runways.
About 1,300 flights had been cancelled Sunday at O'Hare and Midway international airports in Chicago, aviation officials said, and there also were cancellations at Logan International Airport in Boston and Tennessee's Memphis and Nashville international airports.
