Most of southern Ontario is under snowfall warnings.
Snowfall began in southwestern Ontario this morning and Windsor and Niagara are forecast to see up to 15 centimetres, while the greater Toronto and Hamilton area could total between 15 and 25 centimetres between today and tomorrow.
Environment Canada warned that the rapidly accumulating snow could lead to possible isolated power outages, reduced visibility and travel difficulties.
"There will likely be a significant impact on the commute home at rush hour this afternoon in much of southern Ontario."
GO Transit adjusted its schedule due to the storm, as the Greater Golden Horseshoe regional transit operator advised riders to plan for additional travel time. The Toronto Transit Commission said it had plans in place to ensure service was maintained.
Ottawa, Kingston and most of eastern Ontario are expected to experience accumulations of up to 20 centimetres of snow.
Toronto officials are asking residents to stay home unless it is absolutely necessary to leave the house.
"Stay home, work from home, be safe," says Vincent Sferrazza, the city's director of transportation and maintenance.
Salt and cleanup trucks have been out during the afternoon rush hour and have asked drivers to give crews plenty of room and avoid parking on arterial roads.