Nearly 800 people believed to have died in Northwest heat wave

The death count has inched upward since the mercury hit 108 degrees in Seattle two weeks ago. The heat wave is now one of the deadliest weather-related events in Washington state history.

At least 25 people died in King County, and 91 statewide. The numbers could still rise, however, as people are still being found in their homes, and others haven’t recovered from dehydration. The heat wave lasted between June 26 and July 6.

In British Columbia, there were 580 more deaths than expected for this time of year. That's three times the number of deaths the province normally sees each week, according to the B.C. Coroners Service, and reporting from the CBC. In Oregon, at least 116 people died from the heat, according to The Associated Press.

That brings the death toll in the Northwest to nearly 800 people.

Washington's deadliest weather-related disaster was the 1910 avalanche at Stevens Pass, killing 96 people in train cars.

It's also more lives lost than the eruption of Mount Saint Helens – 57 people – and more than the 2014 Oso landslide – 43 people.

The deadliest calamities overall are disease outbreaks of smallpox, Spanish flu, and now Covid-19, with 6,000 deaths.

But no extreme heat or cold temperature event on record has come close to last week's in terms of deaths.

Many parts of the state had never been so hot, in daytime or at night, as they were during the 2021 heat wave.

The heat was especially dangerous for people who didn't have access to a home cooling system.

Under historic heat, amidst a changing climate, dozens of people in Washington died between June 26 and July 6 from ailments including hyperthermia, heart failure, and heat stroke.

Dr. Wayne McCormick, a gerontologist with the University of Washington, said that hydration was the main factor behind heat-related illnesses in people in their 80s, 90s, and 100s.

Older people lose the ability to regulate their body temperature well, McCormick said. Humans tend to keep our bodies regulated to a small range around 98.6 degrees Fahrenheit. But as we age, we lose the ability to regulate our body's temperature; part of that is due to skin thinning and losing insulation.

Washington's Department of Health says it has been difficult to track heat-related deaths so far, since heat-illnesses happened statewide and over several days.

Many of the cases are still under review, and officials in Washington say it could be another month until they have a final count.

Produced for the web by Isolde Raftery.

Correction: Due to an editing error, a previous version of this article included an inaccurate number of deaths in British Columbia. It has been updated to reflect the accurate count.