High pressures trapped hot air in the region, a very unusual meteorological phenomenon.
COVID-19 vaccination schools and clinics closed and a qualifying athletics event for the Olympic Games postponed: Western Canada and parts of the United States suffered historical temperature records on Monday, triggered by a heatwave of unusual intensity.
In Portland (Oregon) and Seattle (Washington State), two large cities in the northwestern United States known for their normally cold and humid climates, the temperature reached its highest level in recorded history (1940).
According to the US weather service (NWS), it reached 46.1 degrees Celsius at the Portland airport at noon on Monday (after a record 44.4 degrees the day before) and 41.6 degrees in Seattle, according to the US weather service (NWS).
But western Canada took the crown, and the town of Lytton, in British Columbia, beat the country's all-time high, with a temperature of 47.9 degrees Celsius on Monday.
Several COVID-19 vaccination clinics were closed, and schools announced the suspension of activities due to extreme heat.
" A prolonged, dangerous and historic heatwave will persist for this entire week, " warned Environnement Canada, issuing alerts for British Columbia, Alberta, and parts of Saskatchewan, Manitoba, Yukon, and the Northwest Territories.
"It's a desert heat, very dry and hot," David Phillips, senior climatologist at Environment Canada, told AFP.
"We are the second coldest country in the world and the country with the most snow," he said. We often see cold waves and blizzards, but we rarely talk about such hot weather ... Dubai will be much cooler than it looks today.
Across the border, Americans are also experiencing high temperatures in the northwestern states. The NWS warned on Monday, "This level of heat is extremely dangerous.
One Seattle market, the Ballard Farmers Market, had to close early, probably for the first time "because of the heat," its manager, Doug Farr, told AFP. "Most of the time, it is because of the snow."
On Monday, Amazon announced that it was opening part of its Seattle headquarters to the public as a refreshment point with a capacity of 1,000 seats. Unfortunately, many homes lack air conditioning in this typically temperate city.
The normal temperature for June in Seattle is 19 degrees Celsius.
"At 21 degrees, it's a good day, everyone is outside in shorts and T-shirts, but this is getting absurd," said a Seattle resident interviewed by AFP, saying it felt " like I was in the desert. ".
Also, in Portland, many residents are taking shelter with mattresses and folding chairs in makeshift air-conditioned places by local authorities.
Not far from there, in the city of Eugene, the last of the athletics events of the American teams for the Olympics had to be postponed on Sunday because of the heatwave.
Extreme heat, with severe drought in the American West, favors multiple weekend fires. On the border of Oregon and California, one of them burned about 600 hectares as of Monday morning, forcing authorities to evacuate some residents and close a state highway.
"Every thousand years"
The heatwave is due to a "heat dome" phenomenon: high pressures trap hot air in the region.
The intensity of this "heat dome" is "so statistically rare that it could only be expected once every several thousand years on average," the Washington Post meteorological experts wrote. "But human-induced climate change has made these kinds of rare events more likely."
According to Nick Bond, a climate scientist at the University of Washington, climate change is certainly a factor but "secondary."
"The main element is this very unusual weather pattern" of the heat dome, he tells AFP. That said, "climate change is real; our temperatures have warmed up here," which has "made this heat event even more severe."