Hydro One said that as of 4:30 p.m. ET, more than 150,000 customers across Ontario were without power. Efforts to restore power would continue through the evening, Hydro One said.
CBC meteorologist Johanna Wagstaffe said there was already more than 10 centimetres on the ground in parts of Montreal by Friday night.
The Major League Soccer game between the Montreal Impact and the Columbus Crew was moved from Saturday to Sunday because of the weather.
"This delay is due to an accumulation of snow on the field and in the stands," a news release from the soccer team said. "The main concern remains the safety of spectators and players alike.
By late Friday, some people in parts of the Maritimes were already dealing with their own blast of snow and ice.
Snowfall warnings were in effect in parts of southern Quebec and a broad swath of New Brunswick.
Nova Scotia was covered by a mix of watches and warnings.
"We're actually under a winter storm watch for Halifax because that snow will be mixing with ice pellets and freezing rain," Wagstaffe said. In other parts of the provinces, areas were covered by freezing rain warnings or snowfall warnings.
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The ice storm moved from southwestern Ontario into the Greater Toronto Area around 10 p.m. ET Thursday. Freezing rain warnings ended around 8 a.m., but continued in areas north and east of the GTA. By Friday evening, the Toronto area was hovering around 4 C and had forecasters said people could expect "periods of drizzle" and cloud.
Freezing rain left sidewalks and roads coated with ice in the small city of Orangeville north of Toronto earlier in the day. Residents could barely walk down the street. Others scraped away thick ice from car windows.
Parts of northern Ontario was also dealing with some wintry weather — a winter storm warning was in effect in Sudbury, with Environment Canada warning that as much as 15 centimetres of ice and snow could fall by Friday night.
Earlier in the day, Air Canada issued weather alerts for five airports it flies through, in Halifax, Montreal (Trudeau), New York (LaGuardia), Ottawa and Philadelphia, warning passengers flights could be delayed or cancelled because of the storm.
Dozens of flights were delayed or cancelled at Toronto's Pearson International Airport.
Bus strikes hydro pole
In Ottawa, an OC Transpo bus struck a hydro pole that had crashed into a ditch along Woodroffe Avenue earlier Friday. No injuries are reported. Road conditions were extremely slippery at the time.
Environment Canada warned of the possibility of high winds in the Ottawa area overnight, saying power outages were a possibility as gusts could hit 60 kilometres per hour.