A winter storm bearing a combination of snow, freezing rain and rain hit parts of Ontario, Quebec and Atlantic Canada on Wednesday, leading to slippery conditions and numerous cancellations of flights and school buses.

At Toronto's Pearson International Airport, more than 140 flights were reported cancelled Wednesday, along with many delays.

Air Canada warned that flights to or from cities in Ontario, Quebec, Atlantic Canada and a large swath of the U.S. northeast could be cancelled due to freezing rain.

Flight cancellations were also reported by airports in Ottawa and Montreal.

In Chicago, a key U.S. transportation hub, airlines cancelled more than 1,000 flights into or out of the city's major airports, O'Hare and Midway.

The big low-pressure system, called a "Texas low," is tracking northeast through the Great Lakes toward Atlantic Canada.

The system's moisture is encountering cold air and forming what Geoff Coulson, a warning preparedness meteorologist with Environment Canada, calls "a messy mix" of snow, rain and freezing rain.

Here's what you can expect in each area:

Ontario

Freezing rain warnings were in place Wednesday for many areas of southern and eastern Ontario, including Kitchener-Waterloo, Guelph, Mount Forest, Newmarket, Kingston, Cornwall, Brockville, Belleville and Ottawa.

Toronto rain, freezing rain

Wet snow turned to mostly rain with ice pellets in Toronto on Wednesday, leading to challenging driving conditions for motorists. Parts of Eastern Canada are also without electricity Thursday morning. (CBC)

Freezing rain was expected to last into the late evening hours in these areas, Environment Canada reported at 7:20 p.m.

"Southwestern Ontario will get mostly rain during the day Wednesday," said Coulson. The rain will transition into snow by Thursday.

In Toronto, early morning freezing drizzle gave way to light snow and then rain again. The rain will turn back to wet snow early Thursday, with some light snow and slightly cooler temperatures later in the day, as well as gusts topping 50 km/h by late afternoon. 

Environment Canada forecast that snow and ice pellet amounts would range from a coating to two centimetres over southern parts of the province and near the Lake Ontario shore. As much as 10 centimetres of heavy snow could accumulate in northern areas inland from the Great Lakes.

Rainfall warnings were in place for regions including Hamilton, Niagara and along the northern shore of Lake Erie. Evironment Canada said total rainfall amounts of 25-35 millimetres were expected and there could be localized flooding in low-lying areas because the ground is frozen, reducing its ability to absorb water.

Ottawa was expected to get five to 10 centimetres of snow and ice pellets Wednesday, transitioning into a longer period of freezing rain Wednesday evening and into Thursday before turning into rain.

Hydro Ottawa on Wednesday warned of possible outages because of freezing rain.

"We are expected to see some prolonged periods of it as we head into the evening hours," Michelle Nelson of the Weather Network told CBC News.

Many school bus cancellations were reported throughout central and eastern Ontario.

Quebec

Southern Quebec was to get snow or snow and ice pellets, and as warmer air moved in and was likely to get an extended period of freezing rain ice pellets late Wednesday and early Thursday," said Coulson.

Hydro-Québec said just after 1 a.m. ET on Thursday that strong winds and freezing rain led to power outages which were affecting about 233,000 customers provincewide. The majority were in Montreal and surrounding areas – with tens of thousands affected in each of Lanaudière, Laurentides, Laval and Montérégie.

A Hydro-Quebec spokesman said teams of repair crews were working to restore electricity, but cautioned that some customers may be without power until Thursday morning, depending on weather conditions.

The Montreal area will get rain Thursday morning, while communities north of Montreal may still be experiencing freezing rain or snow.

Snow will be changing to freezing rain around midnight in central Quebec. The precipitation is expected to switch back to snow by Thursday afternoon.

Atlantic Canada

"The system may begin as snow or freezing rain in some areas, like Nova Scotia, before turning into rain," Coulson said. Nova Scotia can expect as much as 50 millimetres of rain.

Temperatures were set to rise through the night. By very early Thursday, they will range from 6 C to 10 C across the province as rain continues into the morning.

In New Brunswick, where freezing rain warnings were issued Wednesday, the icy drizzle was expected to continue into Thursday morning in some northern regions.

New Brunswick's Emergency Measures Organization issued a weather advisory on Wednesday, warning an extended period of freezing rain could cause power outages and lead to localized flooding. As of 6 p.m. AT, NB Power was reporting 109 customers were without power in the Sackville-Port Elgin area.

In Newfoundland, the storm started as snow, before transitioning to ice pellets and freezing rain, and then rain. In Labrador, it was also to begin as snow before transitioning to freezing rain, with the snow expected to last slightly longer.

Heavy snow in U.S. Midwest

In the United States, the storm was moving through parts of the Midwest and was expected to dump as much as 45 centimetres of snow on some areas.

The National Weather Service issued winter weather warnings Wednesday for an area stretching from Missouri northeast through Illinois, Indiana and Michigan, with blizzard warnings for counties in eastern Illinois and northwestern Indiana.

Winter weather advisories were in place for parts of New York, Pennsylvania and New England.

With files from The Associated Press