On Sunday, the heat buckled roads as Seattle-Tacoma International Airport in Washington reached a record temperature of 104 degrees Fahrenheit, 12 degrees hotter than its previous record of 92, which was set in 2015. And the western Canadian community of Lytton reached 116 on Sunday, an all-time record for the nation and one of 40 records set in British Columbia that day, according to the BBC.

Meanwhile, in Washington and Oregon east of the Cascade Mountains, the heat was expected to endure through the week, after reaching a projected high of 117 on Tuesday. At least 11 towns in northwest Oregon and southwest Washington state recorded all-time high temperatures, many surging past the previous maximums by 4 or 5 degrees Fahrenheit.

Excessive heat warnings covered western maps from British Columbia, Canada, to Montana in the east, and south to the U.S.-Mexico border. The heat wave shattered all-time temperature records on Saturday and Sunday with triple-digit temperatures, according to the National Weather Service. But still higher temperatures were forecast for Monday and Tuesday, as the “unprecedented event” continued to scorch the landscape and put health at risk through the week.

“Dangerously hot conditions today with temperatures lingering in the upper 90s on Tuesday with potentially dangerously hot heat index values up to 111,” said the NWS excessive heat warning that remained in place through Monday and, in some areas, extended into Thursday. “Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities.” Health officials advised people to reschedule outdoor activities slated for Monday, The Seattle Times reported.

The intensity of the heat wave, measured by how far temperatures are spiking above normal, is among the greatest ever measured globally. The extremes are on par with a 2003 European heat wave that killed about 70,000 people, and a 2013 heat wave in Australia, when meteorologists added new shades of dark purple to their maps to show unprecedented temperatures.

And the more extreme the temperature records, climate scientists said, the more obvious the fingerprint of global warming will be on the heat wave. But even among climate scientists, the biggest concern was the immediate impacts of the record shattering temperatures.

“I shudder to think what the mortality rate will be from this event,” said Phil Mote, a climate scientist with the College of Earth, Ocean and Atmospheric Sciences at Oregon State University. Research shows that early season heat waves like this one are deadlier than those happening later in the year because people haven’t acclimatized yet, he added.

Local weather service offices warned people to cool themselves with a reminder that heat was the leading cause of weather-related fatalities between 1991 and 2020. But experts and officials warned that people in the region, where there are fewer people with air conditioning than without it, are ill-equipped to protect themselves from persistent triple-digit temperatures.

North Seattle College climate scientist Heather Price taped aluminum foil inside her windows to try and protect her family of four as temperatures reached the 90s early Sunday morning. She used a handheld thermometer to check how much it cooled their home.

“This really is a public health emergency,” she said. “Of all disasters, heat kills the most people. The data is out there, and it’s worse in cool climates.” Even though Seattle has opened wading pools and spray parks that have been closed since early in the Covid-19 pandemic, some public water fountains are still turned off to prevent spread of the coronavirus.

“Residents are not happy about the failure of access to public water with this heat,” she said.

Where There’s Unprecedented Heat, There’s Fire

Fire meteorologist John Saltenberger, of the Northwest Coordination Center in Portland, keeps an eye on the risk of wildfire across Oregon and Washington.

It’s not only the historic temperatures increasing the wildfire potential, but also what might follow, with winds kicking up across the rangelands east of the Cascade Mountains as the heat wave extends for another week, he said. But Saltenberger’s concerns also extend beyond the current weather patterns to some troubling long-term trends that he was following through the spring.

Never have the three months from March to May been drier in 125 years of record-keeping, he said. He also recalled a climate study that showed how, over four decades, the number of rainy days during the fire season is declining in the Northwest.

“Heat alone isn’t really sufficient to trigger the risk of large costly, fires,” he said. “Heat, overlaid with lightning or heat overlaid with a strong wind event—now that’s a different matter.”

“Less rain during fire season means more hot, dry days, which means higher fire danger and more fires and more burned areas,” he added. “And 2021 appears to be going right along with that trend.”

Oregon had just two large fires burning Monday totalling less than 8,000 acres, and Washington had none, according to the National Interagency Fire Center.

But Saltenberger’s latest seven-day outlook for Washington and Oregon projected that wildfire risk is rising for the drier, inland landscapes in both states east of the Cascade Range. Beginning Wednesday, the probability of large fires triggered by lightning and fueled by a “critical burn environment,” rises to high risk levels, his Monday wildfire forecast said.

“Fire danger indices continue rising as the heat wave amplifies over the entire region,” it said. “Significant fire potential ramps up starting today due to the combination of heat, rising fire danger indices and easterly winds that will eventually switch as a thermal trough moves across the Cascades.”

The U.S. Drought Monitor map showed the entire state of Oregon experiencing some form of dryness last week, with more than three quarters of the state in “extreme” or “exceptional” drought. In Washington state, about one fourth of the land appeared in the “extreme” drought category.

Biologists are hoping to protect Snake River sockeye salmon, which are just beginning to head upstream to spawn, by releasing cooler water from the Dworshak Dam, Oregon Public Broadcasting reported.

The heat wave, following a year of deadly wildfires and a spring dry enough to put 91 percent of the West in drought, is triggering conversations about the ways climate change has already set the stage for more record-smashing weather disasters.

An Underestimated and Underreported Threat

The current Western heat wave is remarkable by almost any standard, said University of Reading climate scientist Chloe Brimicombe. But such events are becoming more common, to a large degree because of the 1.2 degree Celsius global average temperature increase since the industrial revolution has pushed the heat wave needle into the red zone, she said.

“Heat waves are our alarm system for the climate emergency,” she said. “If there are more heatwaves, our emergency is getting worse.”

Some of her recent research shows heat threats are underestimated and under-reported, and that poor, vulnerable communities suffer the most, with developing countries taking the biggest hit.

The Arizona Republic reported earlier this month on the steep increase in people suffering severe burns from surfaces like pavement during heat waves. Over the summer of 2020, the Arizona Burn Center Valleywise Health reported 104 people being admitted with burns from hot pavement, almost all of whom required surgery for their injuries, a fact that shocked Brimicombe. “I hadn’t fathomed the idea of (third-degree) burns (during a heat wave),” she said.

Globally, extreme heat killed at least 166,000 people between 1998 and 2017, according to the World Health Organization. In the United States, the EPA cites studies estimating 1,300 heat deaths occurred annually in recent decades. Federal research shows the heat wave season in Portland and Seattle is 40 to 60 days longer than in the 1960s.

Heatwaves threaten food crops and are already triggering mass migration. They also have ecosystem impacts, such as widespread fish die-offs in dried-out streams and potentially harmful algal blooms in lakes and coastal areas. Extreme heat can drive sudden forest mortality, killing trees already weakened by drought.

Related: Extreme Heat Risks May Be Widely Underestimated and Sometimes Left Out of Major Climate Reports

Karin Bumbaco, a research scientist at the University of Washington who serves as Washington’s assistant state climatologist, called climate change attribution “a really great question, and it is one that’s hard to answer.” She said it won’t be possible to tease apart how much natural variability and how much man-made warming can be blamed for the current Northwest heat wave until scientific studies examine what happened, which typically takes months or years.

“But, you know, even without that being done, it’s a safe assumption, in my view, to blame increasing greenhouse gases for some portion of this event—Washington state is warming, the Pacific Northwest is warming, globally we’re warming,” she said. “As we shift that baseline, we’re going to see more and more of these extreme events.”

For climate scientist Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, the Pacific Northwest extreme heat is shocking. He said on Twitter that scientists will find a clear global warming fingerprint on the heat wave, with the exact influence of global warming linked with how hot it gets.

“And the hotter it gets,” he said, “the larger the attribution will be.”

Scientists with World Weather Attribution have already launched a study to identify how global warming intensified the Pacific Northwest heat wave, with initial results expected in early July, said Geert Jan van Oldenborgh, a climate scientist with Royal Netherlands Meteorological Institute, who has co-authored several previous climate attribution studies.

That research could help explain a worrying trend. In some regions, like northwestern Europe, heat waves in the last 20 years have become warmer about twice as fast as many climate models project, “and we don’t know why,” he said.

Larry O’Neill, Oregon’s state climatologist and associate professor at Oregon State University, agreed the trend in the Northwest is for more extreme heat events and even higher temperatures, based on a growing body of climate research. Temperature records, shorter winters, drought, the doggedness of a heat dome over the West and even tropical cyclone data from the western Pacific—they all point to what’s come to be called the “fingerprint” of global warming on weather, he said.

“These are things that were all projected by climate models 20 years ago, and we’re experiencing them now,” O’Neill said.

For some climate scientists actually feeling the heat, the fact that climate models have been predicting events like the current heat wave for decades means their discomfort is matched by frustration over the unheeded warnings.

“I’m hoping this heatwave is going to wake some folks up,” Price, the North Seattle College climate scientist, said. “People think they are living in the climate they grew up in, but it’s gone. The best we can do now is soften our landing in a heated world.”