TORONTO - The season's first major wildfires have spread to roughly 10 000 ha across Western Canada on Sunday as authorities issued an evacuation order for a community in British Columbia and warned of poor air quality across provinces.

In British Columbia, thousands of residents in Northern Rockies Regional Municipality and Fort Nelson First Nations were evacuated as the nearby blaze nearly doubled to 4 136 ha.

Fort Nelson First Nation, 7 km from the town, also issued an evacuation order for Fontas, an Indigenous community.

Northern Rockies Regional Municipality Mayor Rob Fraser in a TV interview said most of the 3 500 residents in and around Fort Nelson had been evacuated.

Across the border in Alberta, residents of Fort McMurray, an oil hub, faced extensive damage from wildfires in 2016, were asked to prepare to leave.

Alberta said two wildfires were extreme and out of control and recorded 43 active fires, including one located 16 km southwest of Fort McMurray. It grew significantly over the weekend to 5 500 ha, much larger than what was reported on Friday.

On Sunday, authorities said the fire had subdued but was expected to increase as the temperatures soar.

Winds from the southeast are expected to push the wildfire away from a major highway and toward the Athabasca River.

Fraser said the fire was started by a tree blown down by strong winds falling onto a power line.

Six crews of wildland firefighters, 13 helicopters and airtankers were taming the fire on Sunday, said Alberta authorities.

Evacuation alerts were in place for Fort McMurray, Saprae Creek Estates and expanded to Gregoire Lake Estates and Rickards Landing Industrial Park.

Although there is no immediate risk to these communities, the alert ensures residents are prepared to evacuate if conditions change.

Smoke in Fort McMurray on Saturday was coming from fires in northern British Columbia, Alberta said.

Environment Canada issued a special air quality statement that extends from British Columbia to Ontario on Sunday.

Last year, a veil of smoke blanketed the US East Coast, tinging the skies a fluorescent orange as smoke reached parts of Europe as hundreds of forest fires burnt millions of acres of land and forced about 120 000 people to leave their homes.

The federal government has warned Canada faces another "catastrophic" wildfire season as it forecast higher-than-normal spring and summer temperatures across much of the country, boosted by El Nino weather conditions.

Canada experienced one of its warmest winters with low to non-existent snow in many areas, raising fears ahead of a hot summer triggering blazes in forests and wildlands amid an ongoing drought.