In a grim start to a long weekend in Canada, at least six people were killed and hundreds of thousands of customers remained without power after a line of thunderstorms cut a violent path across parts of Quebec and Ontario on Saturday, according to Environment Canada.
The storm — with wind gusts surpassing 80 miles per hour — uprooted trees and damaged power lines and structures across southern and central Quebec and southern Ontario, Environment Canada, the government’s weather service, said.
On Sunday, a day before Canadians were to celebrate Victoria Day, scattered tree limbs still blocked roads and animals were trapped by pieces of splintered barns. Utility companies rushed to restore power for customers, some of whom had been in the dark for more than 12 hours.
The storm was a derecho, a line of severe thunderstorms that produce high winds and can spawn tornadoes, said David Sills, the executive director of the Northern Tornadoes Project at Western University, in Ontario.
That kind of severe weather, which feeds off instability in the atmosphere, is rare in Canada, occurring once perhaps every five or 10 years, he said. But one cutting through heavily populated areas that causes so many deaths is even more unusual, he added.
“It just got stronger and stronger,” Mr. Sills said. “By the time it got about an hour west of Toronto, there was a gust of wind of 132 kilometers per hour,” or about 82 miles per hour.
Most of the fatalities were the result of people being hit by falling trees, the police said.
This included a woman in Brampton, Ontario, just west of Toronto, as she walked outside; a person who died when a tree fell on a camping trailer that was parked at Pinehurst Lake; a 59-year-old man at a golf course; a 30-year-old man in the Ganaraska Forest, east of Toronto; and a 44-year-old man in Greater Madawaska, in eastern Ontario.
In Quebec, a 51-year-old woman died after her boat capsized and she fell into the Ottawa River in Gatineau, just north of Ottawa, the police said.
Mr. Sills said the deaths from falling trees likely stemmed from the nature of the storm, which was moving at more than 60 m.p.h., and that Canadians were outside enjoying the long weekend.
“People didn’t have a chance to take cover if they didn’t have a warning,” he said. “This came upon them very quickly with very little time to react.”
Widespread power outages continued into Sunday evening, with about 226,000 customers, mostly in Ontario, still without electricity. Hydro One, a power company servicing Ontario, said that its transmission system in the Ottawa area had incurred substantial damage.
Jim Watson, the mayor of Ottawa, said in a statement on Saturday that the city had deployed “city and hydro crews” to restore power and clear roads.
“This was a massive storm and we ask for your patience,” Mr. Watson added.
Vimal Patel contributed reporting.