Snow storms in the central US have left at least 22 people dead and tens of thousands without electricity, the Associated Press news agency reports.
The storm reduced visibility to nearly zero in some places
Hundreds of accidents were reported as far south as Texas, where there was a 50-vehicle motorway pile-up.
The storm has also felled trees and power lines and caused the cancellation of hundreds of flights.
More heavy snow has been forecast as the storms move into the Great Lakes region bordering Canada.
The US National Weather Service has issued several heavy snow and winter storm warnings.
Among others, north-central Idaho, western Montana, and western and north-east Wyoming were expected to suffer fresh falls of snow and freezing rain on Monday.
Officials reinforced their warnings to people to stay at home.
"I know it's the holidays but we hope people use some common sense when travelling," said Sergeant Chad Breuer in Wisconsin.
"There are a lot of people saying: 'Ill just leave that much earlier,' but still the roads are not favourable for travelling."
Multiple vehicle pile-ups closed major highways in the central states over the weekend.
In Minnesota alone, there were more than 300 road accidents and at least eight deaths.
At least 12 people died in accidents in Wyoming, Indiana, Wisconsin and Michigan and deaths were also reported in Texas and Kansas.
The fatality in Texas came in a pile-up on Interstate 40.
At least 16 people were taken to hospital, two with life-threatening injuries.
Many in the pile-up were holidaymakers, including families with small children not dressed for the weather, police said.
The storm system had blown out to sea by Monday morning, leaving sunny skies in its wake, but new warnings were out along the shores of the eastern Great Lakes region in both the US and Canada.
Storm warnings for parts of Minnesota, Wisconsin and Michigan were lifted but the authorities said this did not mean safer roads - with interstate routes still icy and rural roads even more dangerous.
In Chicago, around 300 flights were cancelled on Sunday night because of high winds.
Michigan Utilities reported that around 15,700 customers were still without power on Monday morning, although power had been returned to many communities.
The BBC's Matthew Price in the US says Americans expect bad weather at this time of year and the country has the resources to cope.
But for some the fierce winter is making it a miserable Christmas, our correspondent adds.