City officials are relying on salt trucks instead of plows to clear Toronto's ice-laden streets Sunday as southern Ontario is slammed by freezing rain.

Barbara Gray, general manager of Toronto's transportation services division, explained this effort is to prevent flooding when the ice buildup starts to melt as temperatures jump Monday.

"Our interest is ensuring that the catch basins stay clear so that when we have flooding and additional rain that happens later in the day and overnight and into tomorrow, those catch basins can do their job," she said.

City officials are asking residents to clear debris from catch basins to help water enter storm sewers and prevent flooding. (City of Toronto/Twitter)

The freezing rain is expected to turn to rain late Sunday afternoon and "may fall heavily at times," according to Environment Canada. Rainfall amounts between 20 and 25 millimetres is forecast, and up to 35 millimetres could fall by Monday morning. Flooding is possible, due to this, on roadways and low-lying areas, according to the Toronto and Region Conservation Authority.

"If you plow all of that slush and all of the frozen ice pellets onto the side of the road, it dramatically increases the chances that we would have a real flooding problem if we get heavy rains later on," Mayor John Tory told reporters Sunday at the city's emergency management operations centre.

James Kilgour, director of Toronto's office of emergency management, said he is not aware of any flooding in Toronto yet due to the storm. But the city remains under a flood watch.

Ice buildup from the storm made for messy streets and dangerous driving conditions Sunday. (Ousama Farag/CBC)

In the meantime, some 80 salt trucks hit city streets Sunday morning, Gray noted, though only 30 are equipped with plows. During peak winter weeks, the city typically has access to some 200 salt trucks, she said.

"We definitely have fewer plows," she said, explaining city officials are comfortable with the level of equipment on the roads.

"Even when we have access to the number of equipment during the peak winter season, we don't always deploy them. We always right-size the number of vehicles that we have based on the event."

Tory reaffirmed that the city is "well-equipped" to deal with the fallout from the storm despite the fact that remaining winter contracts for non-city plows and salt trucks expire at midnight.

"A lot of people have raised questions about the plowing. The plowing has been done on the expressways in accordance with the city's standards regarding weather events," he said.

'Stay off the roads'

Toronto police saw a rise in the number of single-vehicle collisions Sunday afternoon due to "slippery conditions."

Const. Clint Stibbe, spokesperson for Toronto police's traffic services division, called for cyclists, pedestrians and drivers to steer clear of the roads, if possible, until the storm passes.

Drivers have been losing control, hitting other vehicles, crashing into poles and guard rails and getting stuck on ice or hills, Stibbe said.

"The number of vehicles that are getting stuck is almost as common as the number of collisions," he added.

Ice pellets and freezing rain diminished visibility for drivers along Lakeshore Drive. (Cole Burston/Canadian Press)

Ontario Provincial Police reported 150 crashes in the Greater Toronto Area.

Sgt. Kerry Schmidt, spokesperson for the OPP's highway safety division, predicts road conditions will "deteriorate throughout the day" and urged drivers to cancel all non-essential travel.

"It's not worth it," he told CBC Toronto.

Tory echoed this, urging "those that don't have to go out to work or for other emergencies, please stay off the roads or use public transit."