As fires move across large swaths of British Columbia's dense forests, there are new warnings about air quality in communities as far away as Alberta.

The B.C. Environment Ministry said that the thick smoke is a "very high health risk," and many residents and businesses are keeping their doors and windows shut.

With high winds fanning more than 270 wildfires across the province, the smoke will only get worse for some communities if current weather patterns continue.

"You literally could see the plume of smoke approaching," said Ralph Adams, an air quality meteorologist with the B.C. government.

Flights have been delayed in the southern B.C. city of Kamloops, and in Cariboo Regional District to the north, residents have been dealing with poor air for days.

In Calgary, a smoky haze shrouded the city on Thursday as residents with breathing problems were advised to stay inside. Smoke was also visible in Edmonton and in other towns in Alberta.

"Listen to your body, err on the side of caution. If you don't have to go outside, don't go outside," said Deb Steele, with the Lung Association of Alberta. "Any particulate matter in the air is not good for anyone."

Meanwhile, residents have been asked to stay out of the B.C. backcountry and hundreds of homes have already been evacuated because of the flames.

"Strong winds will fuel existing fires and lightning may spark new fires. In addition, strong winds may prevent air operations and heavy smoke may impair the ability of ground crews to respond," said a statement from the B.C. Wildfire Management Branch website.

Officials will be keeping a close eye Thursday on the weather in an area south of Prince George near Williams Lake.

Still, B.C. Minister of Forests and Range Pat Bell told CTV News Channel that the worst may be over.

"I think the good news is we really made it through what was the most challenging time, the last 24 hours in particular," he said, speaking from Prince George, which he called the centre of the fires.

"We haven't had rain virtually for 60 days and that was coming out of a winter with almost no snowfall," Bell said.

He added that there were a "series of lightning strikes about three or four weeks ago that created a significant number of fires, and then over the last 24 hours, we've had extreme wind conditions."

While conditions are improving and allowing crews to get back onto the ground to fight the fires, some blazes are growing. Bell said that a fire near Burns Lake grew from 9,000 hectares to about 32,000 hectares overnight.

Stephen Waugh, emergency program co-ordinator for the Central Coast Regional District, said some areas are virtual tinderboxes.

"The hardest hit areas seem to be in the Cariboo Chilcotin region where there were extreme fires burning before these winds arrived. So the morning will tell us how things are looking in that region," Waugh said.

The latest evacuation orders affect residents near Meldrum Creek, Meldrum East Fraser, Soda Creek/Williams Lake, McLeese Lake and Westwick Lakes, according to a statement posted Wednesday on the district's website.

Waugh said hot, dry weather and high winds are a bad mix.

Waugh himself has been trapped in Bella Coola for days. The isolated town has just one road in and out, and it has been shut down to traffic since Sunday night.

The hot, dry summer has left some 279 forest fires raging across British Columbia at last count. A full 71 per cent of the province is at high or extreme risk for forest fires, twice as much as last year.

With files from The Associated Press