Portland, Ore.—By noon on Monday, the temperature in Portland was climbing up the triple digits, passing 104, then 106, on its way to a record high of 116—40 degrees higher than the average temperature for this time in June. Most of the city was in a daze, the streets quiet and nearly empty. But one block in the city’s southeast quadrant was busy with cars and people lining up at a shade tent to collect coolers full of water, Gatorade, and other supplies to bring to people living on the streets and in encampments throughout the city.

“We need to make sure that they’re not dying while they’re out there,” said Lou, a volunteer with a local mutual aid group called Defense Fund PDX. The group formed as a bail fund during the protests over police violence last summer, and since then has adapted to respond to other needs in the city, particularly those of the 4,000 people living without housing in Portland. Lou, who asked that her last name be withheld, said the group raised and spent about $37,000 on hotel rooms during winter ice storms. This month, when forecasts predicted life-threatening temperatures across the Pacific Northwest, Defense Fund PDX started putting out calls for donations and volunteers to distribute supplies, while other mutual aid and community organizations set up cooling stations.

Extreme heat has been described as a “silent killer”: Its effects are often harder to see than the sweeping destruction caused by hurricanes, flooding, or wildfires, and the deaths it causes are often hidden, statistically speaking, attributed instead to underlying health conditions like heart disease. But heat kills more people in the United States and around the world each year than any other weather-related disaster, and as the planet warms, heat waves like the one that swept across the Northwest are becoming hotter, longer, and more frequent. Like other climate-related disasters, the risk from extreme heat is felt unequally. Not everyone can afford air-conditioning; urban neighborhoods that are poorer and have more residents of color tend to be hotter than whiter, wealthier neighborhoods in the same city. Among those most at risk are the elderly and people living and working outside. At least one farmworker died during the heatwave, in Oregon’s Willamette Valley, with the preliminary cause listed as “heat.” Two men living on stretch of road in Bend, Ore., were found dead over the weekend, presumably of heat-related causes, one in an RV that someone at the scene described as “a microwave.”

The physical infrastructure in Portland and the greater Northwest was not designed for such extreme temperatures. Roughly a third of the homes in Portland, and more than half of the homes in Seattle, have no air-conditioning. In Washington, sections of Interstate 5 began to buckle. Portland shut down its light rail and streetcar service because of the heat, which was so intense that it apparently damaged a streetcar power cable. Nor were social services and labor protections developed with extreme heat in mind. In Oregon, rules to protect farmworkers and other outdoor workers from dangerous heat—including mandating access to water and shade—have been proposed but were not yet in place over the weekend. The city opened emergency cooling stations for people without housing or whose housing was too hot, but many living outside were reluctant to leave their communities and belongings behind, said Dr. William Toepper, the medical director for Portland Street Medicine, which provides mobile medical care to the city’s unhoused residents.

“It’s like acute disaster on chronic disaster,” said Toepper. And the acute disasters are stacking up: This weekend’s heat emergency felt similar to the wildfire smoke that engulfed the West Coast last fall, Toepper noted. Street medicine teams active during the weekend reported that many people had found resourceful ways to get by in the heat, including by rigging up ice baths, while civil society and volunteer groups mobilized quickly to help vulnerable residents. “It seemed like every time I turned around there were friends and citizens who were going out and doing relief work, and I think that really needs to be applauded,” he said. Still, throughout successive weather-related crises, the underlying vulnerabilities remain. “You can plan all you want but until there are places for people to shelter, what can you do?” said Toepper.

Overnight on Monday, the temperature in Portland dropped 52 degrees—another record. The break in the heat was an immediate relief, but a superficial one. More than 90 percent of the West is still in an unprecedented drought, and the region is bracing for another punishing wildfire season. Some news stories referred to the heat wave as a once-in-a-thousand-years event. But as the Oregon Climate Office noted, “The past is no longer a reliable guide for the future.” What was once rare is becoming routine. So much of what we’ve built is based on old assumptions that no longer apply—and yet the pattern of who bears the brunt of these multiplying crises remains familiar.