Wildfires bore down on two Canadian cities Friday, with firefighters in the west bracing for another "scary" night as stunned refugees from the far north began arriving at shelters after their entire city was evacuated.

The two fronts in British Columbia and the Northwest Territories are just the latest in a summer of devastating wildfires across the country that have forced tens of thousands from their homes and left millions of acres scorched.

The blazes have caused "terrible loss," Prime Minister Justin Trudeau told reporters after meeting evacuees from Yellowknife, capital of the Northwest Territories, as they arrived in Edmonton, Alberta, hundreds of miles (kilometers) to the south with no idea when they may return home again.

Meanwhile the premier of western British Colombia, David Eby, declared a state of emergency there late Friday.

The announcement came as the fire burning west of Kelowna, a town of 150,000 people in the Okanagan Valley, exploded a hundred fold in size to 6,800 hectares over the past day.

Officials described firefighters being forced to pull back and some becoming trapped behind lines while making "heroic efforts" to rescue residents.

"We fought hard last night to protect our community," local fire chief Jason Brolund told a briefing on Friday.

"A significant number of structures were lost," he said, but no injuries or fatalities were reported.

"It was like 100 years of firefighting all at once, in one night," he said, adding that he expected "another scary night tonight" under an eerie glow of the fires.

Thousands of households on Kelowna's west side were ordered evacuated or told late Thursday to be ready to leave at a moment's notice.

"The situation is unpredictable right now and there are difficult days ahead," Eby told a news conference.

- 'Empty' -

In the far north, Yellowknife was a ghost town late Friday after ordering its entire population to leave by the afternoon -- the largest ever evacuation from the region.

Most of its 20,000 inhabitants left by car, snaking along the lone highway connecting the remote capital of the Northwest Territories to southern Alberta province.

The nearest evacuation center is 1,150 kilometers (700 miles) away, in Alberta, where several sites have been set up.

Almost 4,000 people flew out, officials said, with a pilot on one of the relief flights telling Canadian media that the lakeside city was "pretty empty."

Among the exhausted evacuees being ferried to hotels was Byron Garrison, 27, who landed in Calgary late Friday with his girlfriend and a friend, carrying only a small bag with two changes of clothes.

The three looked tired, and scared.

"I feel lost because I don't have any idea what is going to happen now," Garrison told AFP. "We don't know what we'll do now."

It was a sentiment echoed by Katel Koumhawa, originally from Cameroon, who moved to Yellowknife earlier this year.

He made the long drive from the northern city to Calgary to save his car from the flames.

He and his family are "happy" they have been saved, he told AFP.

But "we don't know about tomorrow," he added. "About our lives, our jobs. You don't know if everything will be the same tomorrow."

Yellowknife has not been abandoned: crews remained to erect defenses as the flames approached, while water bombers have been seen flying low over the city and the Canadian military is also helping out.

Several towns and Indigenous communities had already been evacuated. The flight from Yellowknife means half the population of the near-Arctic territory has been displaced.

The confusion and terror of the fires and evacuations have been compounded by Meta's blocking of Canadian news on Facebook and Instagram.

The decision -- made earlier in response to a new law requiring digital giants to pay publishers for articles -- has complicated wildfire information sharing.

Heritage Minister Pascale St-Onge on Friday called the ban "reckless" and demanded Meta lift it "for the safety of Canadians facing this emergency."

- Record-setting wildfire season -

Canada is experiencing a record-setting wildfire season, with official estimates of over 14.0 million hectares (34.6 million acres) already burned -- almost twice the area of the last record of 7.3 million hectares. Four people have died so far.

In addition, the fires have emitted an unprecedented amount of carbon dioxide.

Scientists say human-caused global warming is exacerbating natural hazards, making them both more frequent and more deadly.

"It shows how quickly our climate is changing if a place like Yellowknife, so close to the Arctic Circle, is on fire," Adria McPherson told the CBC while fleeing the fires in the north by car.

The evacuation of Yellowknife is the second time an entire Canadian city has been cleared due to wildfires since 100,000 residents of Fort McMurray in Alberta's oil and gas producing heartland were forced out in 2016.