Warnings were issued about conditions across the mid-west, where temperatures were set to fall below -34C.
The storm, which passed over Canada's Maritime provinces early on Thursday, was blamed for at least 12 deaths.
It dumped nearly 2ft (0.6m) of snow on Chicago, bringing the typically bustling city to a frozen halt.
The city closed schools for a second day in a row, and road authorities tried to clear cars abandoned on snow-clogged roads.
In eastern Canada, schools and businesses were closed on Thursday morning after the storm, which originated in the US state of Texas 3,300km away, dumped some 40cm of snow in parts of Nova Scotia and brought 50km/h (31mph) winds to some areas.
In the hard-hit US state of Oklahoma, three people were killed on Thursday when their vehicle ran off a snowy bridge into a river, the Tulsa World newspaper reported.
US air traffic remained hampered on Thursday as airports struggled to clear snow from runways and recover from widespread cancellations during Wednesday's storm.
By mid-afternoon, 2,502 US flights were cancelled, according to tracking website FlightAware.com, including 402 from Chicago's O'Hare International Airport, one of the busiest in the nation.
Across the north-east, buildings that collapsed under the weight of snow and ice piled on roofs included a school building in Connecticut, an aircraft hangar near Boston and a gas station canopy on Long Island.
In Massachusetts, at least 44 buildings collapsed, mostly flat-roofed commercial buildings, Emergency Management Agency spokesman Peter Judge told the Boston Globe.
In upstate New York, a barn roof fell in, trapping cows inside, the Associated Press reported.
Americans and Canadians are recovering from a monster winter storm that crippled air and road transport, closed schools and destroyed buildings.