The season's first major wildfires have spread to roughly 8,000 hectares 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 fire spread to 2,483 hectares.

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.

Fort Nelson First Nation, located seven kilometers (4.35 miles) from the town, also issued an evacuation order for Fontas, an Indigenous community.

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

Alberta said two wildfires were extreme and out of control, including one located 16 km southwest of Fort McMurray. It grew significantly over the weekend to 5,500 hectares, 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.

The federal government has warned Canada faces another "catastrophic" wildfire season as it forecasts 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.