Environment Canada says a winter storm may "threaten" parts of southern Ontario early this week, with up to 25 centimetres of snow possible for the GTA.
The agency has issued special weather statements for much of southern Ontario.
"As if to remind us that spring has not officially begun yet, Mother Nature is gearing up for a significant winter storm," said Environment Canada on its website.
Snow is forecast to begin over Southwestern Ontario during the day on Monday, then spread over the rest of the region that night and into Tuesday.
Environment Canada said there will likely be 15 to 25 centimetres of snow, with as much as 30 centimetres in the Hamilton and Niagara regions.
Snowfall amounts will likely be less north of the GTA towards Georgian Bay and into the eastern parts of the province.
The snow should ease off Tuesday night in most areas.
Prepare for hazardous travel conditions
Risky travel conditions could be on the way. The snow will be dry and fluffy, meaning localized blowing snow as winds strengthen during the storm.
"This snowstorm has the potential to significantly affect travel due to accumulating snow and blowing snow resulting in hazardous winter driving conditions," said Environment Canada.
Environment Canada said it will likely issue winter storm watches and warnings as the storm track and amounts become more certain.
Meanwhile, an extreme cold weather alert is in effect for Toronto, with current temperatures at -13 C and a wind chill of -21 C.