In Ontario, parts of the province were hit with massive snowfalls while other areas, including the Toronto region, were pelted with snow and freezing rain.
"Toronto is out of the woods in terms of heavy precipitation falling today but falling temperatures still pose a serious threat as any standing water or slush starts to freeze up quickly this morning across much of the Golden Horseshoe," said CBC meteorologist Jay Scotland.
The precipitation was expected to change to rain as temperatures rose, but both drivers and pedestrians were being urged to be aware of a possible flash-freeze in time for rush hour.
A flash freeze warning comes when a steep temperature drop causes water from rain or melted snow to quickly freeze.
A mix of snow and rain in Toronto, and snow further north, produced hundreds of accidents on the roads and highways last evening, including one crash in Brampton which left one man dead.
Local school boards warned parents to check online Monday morning to see if any schools cancelled classes for the day. The Toronto Catholic District School Board said it would release a decision by 6 a.m. ET and the Toronto District School Board warned of potential closures.
Much of Quebec was also facing adverse weather warnings Monday morning. Environment Canada issued winter storm, freezing rain and wind warnings for most of the province.
Air Canada and West Jet issued travel advisories for passengers flying Monday, warning flights may be delayed or cancelled because of the winter storm. By Monday morning, dozens of flights going into and out of Pearson International Airport in Toronto had been delayed or cancelled.
Newfoundland power outages
Meanwhile, about 90,000 Newfoundland Power customers were without electricity Sunday night after a power plant went offline in the latest power problem to hit the province in recent days. By Monday morning, that number had dropped to about 30,000
Residents and businesses throughout Newfoundland and Labrador were told to conserve energy as the province grapples with rolling power outages.
Aging infrastructure, a terminal station fire and a blizzard that ripped through the province Friday night combined to overburden an already stretched electricity grid, according to Premier Kathy Dunderdale.
At the peak of the power outages Saturday morning, about 190,000 customers were in the dark, Newfoundland Power said.
"Atlantic Canada is a real mess ... with freezing rain warnings for New Brunswick, P.E.I. and northern Nova Scotia, where I see the risk of freezing rain continuing this morning as a warm front pushes north," Scotland said.
"For much of the Maritimes, this will switch over to rain through the morning and early afternoon ... and further east warnings are out for Newfoundland who deal with this mess tonight through tomorrow — gusty wind, freezing rain and heavy rain."
Prairie deep freeze
Meanwhile, much of Saskatchewan and Manitoba are under extreme wind chill warnings, where residents are facing temperatures that feel as cold as –40 C with wind chill.
"To the east, wind chill warnings are out from Hanna in eastern Alberta through southern Saskatchewan [and] Manitoba," Scotland said.
"Across this warned area, current temps are well into the –30s C with wind chills well into the –40s."
The potentially record-low temperatures are heightening fears of frostbite and hypothermia.
"Persons in or near this area should be on the lookout for adverse weather conditions and take necessary safety precautions," warns Environment Canada.