Experts say the unprecedented heatwave is result of the climate change.
Wildfires were burning across more than one million acres of the western United States and Canada, as scorching temperatures held their grip on areas reeling from a brutal weekend heat wave.
Some 850,000 acres were on fire in the United States — mainly in western states such as Oregon, California and Arizona — while more than 300,000 acres smouldered in Canada's British Columbia alone, according to wildfire officials.
A fallout of clime change
After a brief lull from late June's previous heat wave, extreme temperatures in recent days reached as far inland as the edge of the Rocky Mountains — part of a dramatic trend that experts attribute directly to climate change.
A study by a group of leading climate scientists found that those conditions would have been "virtually impossible" without human-caused climate change.
The World Weather Attribution group said that global warming, caused by greenhouse gas emissions, made the June heat wave at least 150 times more likely to happen.
The scorching conditions saw the all-time record daily temperature broken three days in a row in British Columbia.
Last month was the hottest June on record in North America, according to data released by the European Union's climate monitoring service.
The US National Weather Service (NWS) warned dangerous temperatures were continuing in the region for the early part of the week, with temperatures up to 116 degrees Fahrenheit (47 Celsius) recorded in southern California on Monday, and a heat advisory issued for communities outside Los Angeles.
Across the border, temperatures of around 98 degrees F — well above seasonal norms — were recorded north of Vancouver in British Columbia, where some 300 wildfires were active across the Canadian province.
In California — where more than twice as many acres have burned this year compared to the same point in 2020's record-breaking season — a large fire near Lake Tahoe expanded, spurred by the heat, increased winds, low humidity and dry vegetation.
Large areas of forest have burned, with reports of homes destroyed in multiple towns and footage from the area showing burnt-out, abandoned cars and buildings.
As the state enters what are traditionally its most dangerous months for wildfires, evacuation orders were also issued for the River Fire, which began on Sunday just south of the Yosemite National Park.
In the neighbouring state of Oregon, the even larger Bootleg Fire more than tripled in size since Friday, reaching more than 150,000 acres and threatening power supplies to California.
Two firefighters were killed in an aviation accident in Arizona.
The past six years, including 2020, have been the six warmest on record.