108.

That’s the new measure for the hottest day in Seattle.

Temperatures at Seattle-Tacoma International Airport on Monday afternoon eclipsed Seattle’s previous record of 104, set on Sunday, bringing a dangerous and unprecedented heat wave to a crescendo in a wilting city.  

Temperatures could drop at a record rate as a surge of marine air brings a measure of relief early Tuesday morning.

For those without air conditioning, it’s unlikely to provide deliverance. Typical high temperatures check in around 74 degrees this time in June, according to Matthew Cullen, a National Weather Service meteorologist in Seattle. 

Highs in Seattle Tuesday are expected to be in the 90s, Cullen said, adding that there would be “plenty of sun.”  


And east of the Cascades, temperatures will only intensify on Tuesday, when they will peak. Meteorologists say temperatures could match and perhaps exceed the state’s record of 118.

The heat wave has sent dozens to emergency rooms in Seattle; fouled the air with ozone; primed the state for wildfire; buckled roadways, causing traffic jams; and set the stage for disaster for northwest salmon. 

Advertising

The full scale of its human health impacts won’t be known for weeks or months, said Dr. Jeff Duchin, health officer for Public Health – Seattle & King County, adding that heat can stress underlying health conditions.

“It will take a while to study the increase in those conditions,” he said.

Low-pressure heats us up, then cools

The heat wave’s intensity was amplified Monday by a thermal trough — a low-pressure weather system — that moved across the Olympic Peninsula and into the region, drawing hot, dry air through the Cascades and into Seattle, Cullen said.

Marine air, chasing that system, was expected to seep into Seattle in the middle of Monday night, causing temperatures to dip as low as the mid-60s.

Seattle’s biggest difference between one day’s high temperature and the next day’s low temperature is 43 degrees, according to Joe Boomgard-Zagrodnik, a postdoctoral researcher in agricultural meteorology at Washington State University.

The overnight temperature swing Tuesday morning could approach that mark, but ultimately the sea air will replace extreme heat with merely abnormal warmth.

Advertising

“By Wednesday and Thursday, we’re looking at high temperatures only in the 80s. Still warm for here, but not close to the dangerous heat we’ve seen the last several days,” Cullen said. 

The thermal trough will march eastward on Tuesday, sending temperatures east of the Cascades to their peak, said Joey Clevenger, a National Weather Service meteorologist in Spokane. 

“We’re going to be close to breaking the all-time record,” Clevenger said. 

Clevenger said weather models show temperatures in the Moses Lake and Tri-Cities areas could reach 118.

Washington has seen temperatures rise that high only twice — at Wahluke on July 24, 1928, and at the Ice Harbor Dam on August 5, 1961, according to the state climatologist’s office. Preliminary data from the National Weather Service suggests two Washington weather stations — one in Dallesport and another near the Sol Duc River — hit 118 degrees Monday.

Scientists say climate change’s fingerprints are plainly visible and help explain the intensity of this high pressure event. 

Advertising

Climate change has increased baseline warming and the potential for extremes, said Ben Zaitchik, a climate scientist and professor at Johns Hopkins University who studies extreme events.

The prolonged drought across the West, which Zaitchik said is spurred by climate change, is reinforcing the surface heating allowed by the high-pressure system. 

Streets, water supply strained

High temperatures revealed tension on Washington’s infrastructure as roads crumbled and communities asked residents to cut back on water use.  

Concrete panels on freeways crumbled in the heat Monday, an unprecedented breakdown that caused sudden traffic jams. The Washington State Department of Transportation on Monday closed some lanes of I-5 for emergency repairs. 

Morgan Balogh, an assistant regional administrator, blamed the sudden damage mainly on the declining pavement, which is more than 55 years old, cracked and rutted by heavy trucks and nonstop traffic. Triple-digit temperatures caused these already weak concrete panels in north Seattle and Shoreline to push against each other and buckle upward, he said.

“We get buckling of the freeway when it’s hot — but not like the last few days,” Balogh said. 

Sponsored

Marysville required residents to curtail water use, in part because of high demand during Monday’s heat wave.

The demand, along with a pump that failed at Stillaguamish Ranney Well, caused “concern trends” for the city’s water supply, the city said Monday afternoon.

Customers were told to limit all nonessential household and recreational water use, like filling swimming pools or watering lawns. Residents were asked to delay laundry and dishwasher usage, if possible, the city said.

Prepare for wildfire smoke

The heat wave has primed Washington for wildfire. 

“Be prepared for the smoke to hit,” said Vaughn Cork, a fuels analyst with the Washington Department of Natural Resources, saying the heat wave was “baking things and getting it all ready to go for the next hot and dry event we have to take off.”

A healthy snowpack is insulating vegetation at elevations above 5,000 feet, but the state’s low-elevation forests and grasslands are as dry as they would typically be by the end of July or early August, Cork said.

March and April were the fourth driest on record in Washington State since 1895, according to the state Department of Ecology.

Advertising

The heat wave erased the impact of rainy days in May and earlier in June. 

Much of the state, including the Puget Sound region west of the Cascades, was under a red-flag warning Monday, meaning that fires could spread quickly.

“Any kind of spark or ignition could produce a decent fire,” Clevenger said.

An air quality alert was in effect Monday for parts of King, Pierce and Snohomish counties, not because of wildfire smoke, but because of pollution caused by the heat. 

Sunlight can intensify chemical reactions that create surface-level ozone, which can trigger health issues like chest pain, coughing and congestion. Ozone levels spiked Monday and should decrease Tuesday as temperatures drop, according to the Puget Sound Clean Air Agency.

And the intense heat spells danger this summer for fish and trees.

Advertising

On the Columbia and Snake Rivers, temperatures are already within two degrees of the slaughter zone of 2015, when half the sockeye run was lost due to high water temperatures. An estimated 250,000 sockeye died that year long before reaching their spawning grounds.

The sockeye run is at its peak right now just as temperatures are climbing. Spring and summer chinook and steelhead migrating in the rivers also are at risk.

“We are crossing the line to temperatures that can be disastrous for fish,” said Michele DeHart, manager of the Fish Passage Center, which monitors and studies fish migration in the Columbia and Snake Rivers. “I would say the outlook is pretty grim.”

The drought — and a helping of historic heat — also has amplified the stress on trees, which become more vulnerable to bugs, pathogens and fire.

Public health toll

The heat wave’s impacts on public health won’t be fully understood for weeks or months.

On Sunday, 91 King County residents visited emergency departments for heat-related illness, according to an email from Public Health – Seattle & King County spokesperson Gabriel Spitzer. 

Advertising

Of those visiting emergency rooms Sunday, 22 were admitted to hospitals, and doctors diagnosed 11 with acute kidney failure, 11 with encephalopathy and seven with fever. 

Some 40 patients visited ERs on Saturday, Spitzer wrote. 

But Duchin, the health officer, said emergency visits hardly begin to describe the heat wave’s toll on health. 

Heat can exacerbate underlying conditions, such as diabetes, renal disease and cardiac disease. Heat over several days can have a cumulative effect.

“Your resilience to bounce back is decreased over time as the extreme heat progresses,” Duchin said.

Climate change has a disparate impact on communities and that’s made bare by heat, Duchin said. Less affluent communities often have a higher proportion of people with underlying health conditions. They could have less access to air conditioning and more people who work outside. 

In an interview Monday, Gov. Jay Inslee said the heat wave, like COVID-19, was “another eye-opener on inequalities in society.” 

Advertising

Heat waves are a test of the social fabric of society, said Zaitchik, the Johns Hopkins University professor. 

Heat stress, in general, is relatively easy to avoid even without air conditioning when people are helping one another, and in particular those most vulnerable, to stay cool.

After tens of thousands died in a heat wave in Europe in 2003, including many elderly people, “there was a lot of soul searching,” Zaitchik said, about air conditioning and also why no one had been there to help.

“Climate change — it’s a stressor on our physical system and natural system. It’s a stressor to our social system.”

Seattle Times staff reporters Paige Cornwell, Lynda Mapes and Mike Lindblom contributed to this story.