Heavy snow blanketed parts of Ontario and Quebec Friday, and a storm system headed north from the U.S. resulted in some travel delays during the busy holiday season.

"Today is officially the start of winter, and we're getting hit — and hit hard with snow," CBC weather specialist Craig Larkins said Friday afternoon as he described the weather in some parts of Ontario and Quebec.

Environment Canada had winter storm warnings in effect around Sudbury and parts of eastern Ontario on Friday afternoon, including the Ottawa area. Winter storm warnings were also in effect for a broad stretch of southern Quebec.

Hydro Quebec said at 4:30 p.m. Friday that more than 18,000 people in western Quebec were without power. A Hydro One map showed there were also scattered outages in eastern Ontario.

As the low-pressure system from Colorado, also called the Colorado Low, churned northeast, the National Capital Region got a blast of wintry weather. CBC Ottawa climatologist Ian Black said that as of noon Friday, 21 centimetres of snow had fallen in the city. The snow was expected to continue through the night and into Saturday morning.

"This is where the nasty weather is, Ottawa and east [of Ottawa]," CBC meteorologist Jay Scotland said Friday. "And we're looking at that heavier snow really working its way through southern Quebec.… It's a messy one today thanks to this [Colorado] low. If you are travelling, do check for travel delays."

At Toronto's Pearson International Airport, there were dozens of cancellations of inbound and outbound flights during the busy travel day. At 7 p.m. ET, the online tool showed that most evening departures from Pearson were leaving as scheduled, but there were still many delays and some cancellations listed for inbound flights. The busy international airport expected more than 100,000 people to pass through on Friday.

The Ottawa airport and Montreal-Trudeau Airport also had some delays and cancellations.

“It’s already looking like one of the busiest travel days of the year,” CBC reporter Trevor Dunn said from Toronto's Pearson airport on Friday morning. “Check-in lines are long here at Terminal 1 … but on the whole, flights look like they're moving well right now."

The delays weren't only in Canada. In Chicago, aviation officials said more than 350 flights were called off at O'Hare International Airport on Thursday and more than 150 at Midway International Airport. But on Friday, as the storm continued its crawl eastward, only about 50 flights were cancelled and a similar number faced delays of up to two hours at the Chicago airports.

Downtown Toronto will avoid the worst of the winter storm, but lake effect snow bands are expected off Lake Huron and Georgian Bay, Scotland said Friday. Montreal can expect mostly rain and wind, he added.

In Ottawa, however, the wintry blast led to more than 100 collisions on roads throughout the city Friday morning, according to city and provincial police. All Ottawa school bus services were cancelled, but schools in both the public and Catholic boards remained open.

In Atlantic Canada, mainly rain and wind are forecast for Friday and Saturday, Scotland said, but this could turn to snow in some parts by Sunday as the temperatures drop.

Newfoundland and Labrador will not see much of this storm until late Saturday, with freezing rain possible, but it will be primarily rainy and windy Sunday, with some snow to the north for Labrador, he added.

Snow removal equipment push snow behind the Parliament buildings in Ottawa, as the first storm hits bringing snow and rain to the capital Friday. (Fred Chartrand/Canadian Press)

People in Western Canada can expect much calmer weather.

Vancouver, which received an uncharacteristic 20 centimetres of snow earlier this week, can expect mild precipitation with a high of 5 C, said Scotland.

However, more snowfall is expected for the B.C., with a messy mix of rain and snow showers for the coast, he added.

In Alberta, snow is tapering off, but the temperatures are frosty, Scotland said.

In Saskatchewan, expect flurries n Saskatoon, but slightly above seasonal temperatures in the southern portion of the province, he added.