The City of Toronto is under a snowfall warning starting Wednesday evening, Environment Canada says.

Up to 20 centimetres of snow could fall Wednesday night before tapering off by Thursday evening, the federal weather agency said in a snowfall warning. 

The snow could cause a significant impact on rush hour traffic, causing low visibility at times and blowing snow, according to the alert.

Similar warnings are also in effect for much of southern Ontario, including York, Durham and Peel regions. Slightly more snowfall is expected just outside the Greater Toronto Area near Port Hope and in the Niagara Region.

Residents are asked to prepare for quickly changing and deteriorating travel conditions.