A mixed bag of snow, freezing rain and drizzle blanketed much of southern Ontario on Wednesday as a storm that moved its way north from the U.S.

Environment Canada is warning of "significant" amounts of rain, snow, ice pellets and freezing rain could cause flight cancellations, power outages and rising water levels in Ontario, Quebec and the Maritimes.

Environment Canada has issued wide-ranging freezing rain and winter storm warnings, predicting that the precipitation could cause icy build-up on roads, buildings and electrical wires in some areas.

In Ottawa, "significant ice build-up due to freezing rain" could cause "widespread utility outages," Environment Canada said in a warning.

Residents were experiencing the full force of the storm Wednesday afternoon.

“It's crazy, it’s so up and down,” said one woman, Caroline Murphy. “It’s hard to dress properly, it’s hard to get to work. I had to leave half an hour early this morning.”

The city says all of its sidewalk-clearing equipment is in use, as well as 185 trucks to plow and salt the snowy, slushy, icy streets.

“The salt generally helps prevent bond of snow and ice to the asphalt,” said road services manager Luc Gagne. “We’ll try to get around as best we can and as quickly as we can.”

Although maintenance teams are out in full force, dozens of crashes have already been reported, including one truck rolled over onto its side. Police are warning drivers to slow down if the conditions warrant it.

“If you drive according to the weather conditions, slow down and give yourselves space and time, you will come home,” said Const. Marc Soucy of the Ottawa Police Service.

Environment Canada is predicting up to 20 millimetres of freezing rain in the capital, and says residents should beware of branches or electrical wires that might snap under the weight of the ice. It's also urging residents to avoid travel.

Some school buses in the area were cancelled and by 12 p.m. ET Wednesday the road conditions were beginning to deteriorate.

The peak of the storm is anticipated to hit later in the afternoon, when snow is expected to change to freezing rain.

Meanwhile, Air Canada warned travellers on Wednesday that freezing rain could cause "flight delays and possibly cancellations" at airports across the region, including in Charlottetown, Fredericton, Moncton, Montreal, Ottawa, Quebec City and Toronto.

The airline said customers willing to rebook their flights can do so without incurring any penalties.

WestJet also issued travel advisories for winter storm systems in New York, Southern Ontario, Montreal, and Quebec City, and Porter Airlines issued a weather advisory for the area as well.

In Toronto, freezing rain began falling on the city early in the day, which eventually changed over to rain by the afternoon, leaving a slushy mixture on roadways and sidewalks.

The winter weather forecast prompted a Watershed Safety Conditions Statement, warning of high-flowing water, unsafe river banks and other dangerous conditions.

"This significant amount of precipitation in the form of a mixture of snow, frozen rain and rain will result in higher than normal water levels and flows," the statement said. "The combination of slippery and unstable banks, unsafe ice and cold water temperature will create hazardous conditions close to any river, stream or other water body."

While significant flooding is not predicted, the statement urged residents in the Toronto area to exercise caution around rivers and streams.

North of Toronto, a number of communities were under a winter storm warning, with snow and ice pellet amount of up to 20 cm expected to fall by Thursday afternoon.

According to Environment Canada, the nasty weather is part of a low pressure system that moved up through the Southern United States and toward the Great Lakes on Tuesday and early Wednesday.

Freezing rain warning are issued when rain falling in below-zero temperatures causes ice to build up on outdoor surfaces.

With a report from CTV Ottawa