Environment Canada has issued a special weather statement warning of heavy rainfall, heavy fog and possible flooding in parts of Ontario.
The national weather agency says between 15 and 40 mm of rain could fall in some regions, with locally higher amounts possible due to thunderstorms.
The rainfall comes as southern Ontario experiences unseasonably mild temperatures.
Toronto set a new daily high temperature record of 17.4 C, the warmest for the date in more than a decade, breaking the previous record of 16.7 C set in 2012, according to Anthony Farnell, Global News chief meteorologist.
The rain, combined with spring-like temperatures, is expected to melt much of the existing snowpack from this season’s extreme winter weather, according to Environment Canada.
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Environment Canada says the warm stretch is expected to continue into Wednesday, with sunshine forecast Monday and temperatures between 10-17 C.
Several rounds of showers and isolated thunderstorms are expected to continue through Saturday evening in southern Ontario.
Frozen ground will limit the amount of water that can be absorbed, increasing runoff and raising the risk of flooding in low-lying areas.
Motorists are urged not to drive through flooded roads and to watch for washouts near rivers and creeks.
The weather agency says residents looking for more information on flooding should consult their local conservation authority or the Ontario Ministry of Natural Resources.
In some areas northwest of Toronto, near-zero visibility in fog is also expected.
Environment Canada says locally dense fog should dissipate later in the day as winds become southwesterly, but travel could be hazardous in some locations with visibility suddenly reduced at times.
Residents are encouraged to monitor alerts and forecasts issued by Environment Canada.
–with files from the Canadian Press
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