Canada’s wildfire plague widened on Friday, with most of Yellowknife’s 20,000 residents fleeing ahead of a deadline to evacuate, while blazes hundreds of miles away threatened Kelowna, a much larger city in British Columbia.
The mass migration from Yellowknife, the capital of the Northwest Territories, was the biggest mandatory evacuation so far in Canada’s summer of wildfire disasters.
It remained unclear precisely how many of Yellowknife’s residents had heeded the order to vacate by noon as an encroaching fire loomed. But officials said most stores had closed and that the hospital was offering only emergency care, its patients having been flown to facilities elsewhere.
By late Friday, the line of cars and trucks that had snaked down the only highway to refuge after the evacuation was ordered on Thursday had become a trickle, television footage showed.
In Kelowna, a major resort area, homes on its suburban fringes were on fire and orders to evacuate were decreed in a community where several homes were destroyed on Thursday night.
The blazes amplified Canada’s image as an epicenter of wildfires in a year of record heat around the world, which scientists widely attribute at least in part to climate change. Canada has reported a record number of wildfires this year, with more than 5,700 burning from one end of the country to the other, some of them sending choking smoke into large parts of the United States.
Rebecca Alty, Yellowknife’s mayor, told the Canadian Broadcasting Corporation that more than 5,100 vehicles had exited the city, and about 3,500 people had flown out on a combination of commercial, chartered and military planes. She emphasized that the only road to safety was at risk because of the fire.
“This fire has been burning for the past month so residents are aware of how the highway can open and close at a moment’s notice,” she told the broadcaster, adding that most of the city’s citizens were leaving “voluntarily and willingly.”
Addressing those residents reluctant to go, the mayor warned holdouts that all services and shops, including grocery stores, were now closed and that fire officials anticipated that the city would likely be enveloped in dense choking smoke.
While firefighters were powerless to block the smoke, the city has taken several steps it hopes will keep the fire out of Yellowknife. It is expected to reach the city limits by the weekend.
About 370 acres of trees were felled to create a buffer zone between the fire and city. Sprinklers are dousing the area with 1,000 gallons of water an hour as planes called waterbombers unload more water and fire retardant chemicals.
Members of the Canadian Armed Forces were assisting the local authorities to create fire breaks around the western part of Yellowknife and Dettah, a nearby hamlet, Bill Blair, minister of national defense, said at a news conference on Friday.
“This has been a very difficult summer for people across this country,” said Prime Minister Justin Trudeau of Canada after meeting with evacuees in Edmonton, Alberta, on Friday evening. adding that among those who had fled the fire he found that “the sense of community is incredibly strong.”
In British Columbia a fire that started on Aug. 15 made its way into a residential neighborhood of West Kelowna, a suburban municipality in the area, which has a metropolitan population of about 200,000 people.
Fire officials said that there was “significant structural loss” in a West Kelowna neighborhood on Thursday night although they had no count for the number of buildings destroyed. Houses remained under threat or on fire late Friday.
“It was a devastating night,” Chief Jason Brolund of the West Kelowna Fire Department told reporters. “We fought a hundred years of fires all in one night.”
Chief Brolund said that at some points police officers who had been ordering people to evacuate became trapped by the fire and had to be rescued. Other people went into nearby lakes to avoid the fire.
Strong wind arrived on Thursday, expanding the Kelowna area fire and impeding efforts to control it. Embers were carried over Okanagan Lake, setting off spot fires within the city of Kelowna that were largely extinguished.
On Friday afternoon, W. Bruce Ralston, the minister of forests in British Columbia, told a news conference that the weather was unlikely to provide relief.
“We remain in the midst of a strong weather pattern that is creating sustained winds and dry lightning,” Mr. Ralston said. About 4,500 people were under evacuation orders as of Friday afternoon, while 23,500 people have been told to be ready to pack up and leave.
Pablo Rodriguez, Canada’s minister of transport, told a news conference that the decision by Meta to block news from Facebook users’ feeds in Canada had hindered the ability of residents of Yellowknife to be informed about the evacuation. The social media company took the step after Canada passed legislation requiring Meta to compensate news organizations for the use of their material.
Some residents in community Facebook groups found workarounds by pasting news article links, with added spaces or text in the link to bypass the block, and adding instructions on how to restore them.
Mr. Rodriguez said the government would ask Meta to end its block, calling it “unacceptable.”
Meta did not directly address Mr. Rodriguez’s criticism in an emailed statement. But the company said it has switched on an emergency service for the Yellowknife and Kelowna fires that allows users to find “reputable information, including content from official government agencies, emergency services and nongovernmental organizations.”
The air quality in Yellowknife was expected to deteriorate over the weekend, said Terri Lang, a meteorologist at Environment and Climate Change Canada, a federal agency. A high pressure system might curb gusting winds, Ms. Lang said, but there would be “very little chance of rain.”