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Western Canada faces 'extreme' heat wave, with soaring temperatures raising fire risk

A heat wave that's expected to push daytime temperatures 10 to 15 degrees above seasonal norms is raising the wildfire risk in Alberta and British Columbia, where crews are already battling early-season blazes.

A heat wave that's expected to push daytime temperatures 10 to 15 degrees above seasonal norms is raising the wildfire risk in Alberta and British Columbia, where crews are already battling early-season blazes.

The hot, dry conditions will prime forest fuels for ignition, said University of British Columbia weather and wildfire researcher Chris Rodell, who's concerned that lightning could spark fires after a ridge of high pressure linked to the heat wave breaks down next week.

As the heat eases, Rodell said he expects instability in the atmosphere could lead to thunderstorms and strengthen winds sometime Tuesday or Wednesday.

The Alberta government declared a provincial state of emergency last weekend in response to fires that have forced thousands of people from their homes, and Rodell said the wildfire situation is also heating up in northeastern B.C.

He said temperatures in some areas look poised to exceed seasonal norms by about 10 degrees, a magnitude he described as extreme.

Environment Canada issued a special weather statement for much of B.C. on Wednesday, saying daytime highs in the Interior will be 10 to 15 degrees above seasonal averages, while overnight lows will be five to 10 degrees above normal.

John Cragg, a meteorologist with the weather office, said the heat is coming from a "blocking pattern," when the normal fluctuation of low and high pressures stops, and warm air flows into an area without relief from an influx of cooler northern air.

The forecast shows temperatures are expected to hit 30 C and higher in parts of Alberta that are already grappling with early season wildfires.

There were 80 active fires on Wednesday, with most of the 26 blazes classified as burning out of control clustered in the western half of the province.

Colin Blair, director of the Alberta Emergency Management Agency, said the number of evacuees had fallen to below 18,000 from about 24,000 the day before.

The temperature is expected to hit 31 C in Edmonton on Monday, 30 C in Peace River and 29 C in Grand Prairie.

Special air quality advisories have been issued in response to wildfire smoke for most of Alberta, as well as central and northeastern B.C.

The heat is expected to settle in Friday and intensify over the weekend in B.C., where there were more than 40 wildfires on Wednesday.

B.C. Emergency Management Minister Bowinn Ma said officials are not currently anticipating a heat dome like the one that killed hundreds of people in 2021.

But she said the government will be closely monitoring conditions throughout the province, as elevated temperatures can still affect vulnerable people.

Ma said heat domes are a specific meteorological phenomenon characterized by persistent high pressure that caps heat over an area for a prolonged period.

A heat dome typically keeps temperatures from dropping overnight, something that's not expected during the coming heat wave, she told media at the legislature.

Rodell said the coming heat wave doesn't appear to share all the same atmospheric features that led to the heat dome and its record-breaking highs.

Environment Canada is forecasting the mercury will hit 28 C on Sunday and 30 C on Monday in Fort St. John, where a 29-square-kilometre wildfire is burning nearby.

The Peace River Regional District has issued an evacuation order for several dozen properties northwest of Fort St. John, while others are on alert.

There are two other wildfires of note burning in the province, meaning they're either highly visible or pose a potential threat to public safety.

The BC Wildfire Service has measured one of those fires at 59 square kilometres, spanning the boundary between B.C. and Alberta.

The other is an 11-square-kilometre blaze near the Village of McBride, southeast of Prince George, where the temperature is expected to hit 33 C on Sunday.

Temperatures are expected to be a few degrees cooler closer to the coast, hitting 26 C in Vancouver that day and 28 C in Victoria. Both are more than 10 degrees above historical averages.

This report by The Canadian Press was first published May 10, 2023.

The Canadian Press