"We have restored power to just over a third of the people affected by the ice storm outages," electricity provider Hydro-Quebec said.
About 630,000 homes in Quebec remained in the dark by mid-morning Friday, down from 1.1 million at the height of the outages.
The utility company estimated it would be able to restore power to most customers by midnight Friday but said some homes would be without electricity until Sunday, potentially Monday.
More favorable weather conditions as Friday progresses should "accelerate the restoration of service," said Hydro-Quebec spokesman Regis Tellier.
Montreal, which accounted for about half of the outages, opened six temporary emergency shelters where residents without power spent the night Thursday into Friday.
The storm affected Quebec and Ontario, Canada's two most populous provinces.
An Ontario resident was killed by a falling tree on Wednesday, while a man in his 60s died Thursday morning, crushed by a branch he was trying to cut in his yard, about 60 kilometers (35 miles) west of Montreal.
Hundreds of Montreal city employees were still cleaning up debris Friday, especially in parks where many branches had collapsed under the weight of the ice.
Temperatures of around one degree Celsius (33 degrees Fahrenheit) melted the ice, but wind gusts were shaking trees, risking more fallen branches.
Authorities were still advising people to stay away from power lines.
The power outage was the biggest in Quebec since an ice storm in 1998, which threw the province into chaos for several weeks.
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