A winter storm warning has been issued for regions southwest of Toronto, while commuters in the GTA should be bracing for a heavy snowfall during the commute home.
Environment Canada is calling for between 30 and 50 centimetres of the white stuff to blanket Hamilton and Niagara Falls on Tuesday, while Oakville and Burlington could see a major dumping as well.
In Toronto, where temperatures called for a high of -12C but -26C with the wind chill, forecasters predicted 15 to 20 centimetres of snow when flakes begin falling mid-afternoon.
The weather system is being labelled the worst storm of the season.
Toronto so far has been relatively snow-free, as only 10 centimetres has fallen this winter, the lowest tally at this time of year since 1937.
The city usually accumulates 77 centimetres by this date.
The weather has caused some flight delays and cancellations at Pearson International Airport. Officials say they are prepared.
"We're ready for whatever kind of weather we get and we're confident things will go relatively smoothly," said Greater Toronto Airport Authority spokesperson Scott Armstrong.
Those who plan on flying in the next few days are being advised to call their airline to see if their flights have been delayed or cancelled.
The Wednesday morning commute could be treacherous as well as another 10 centimetres of blowing snow is expected.
The snowfall is finally expected to end Wednesday night.
Police are reminding residents to use caution while shoveling following the death of an Orillia man. The 43-year-old suffered a heart attack while clearing snow from the roof of his parents' home.
Meanwhile, the City of Toronto extended its extreme cold weather alert on Tuesday.
With a report from CTV's John Musselman
