Last year’s heat wave was a wake-up call for many in the Pacific Northwest.

The infamous “heat dome,” which brought unbearable heat to a region not known for it, provided a bitter incentive for Washington state residents to learn from and adapt to the growing impacts of climate change.

The secret to staying cool during a once-in-a-millennium heat wave, according to new research, can be as simple as good ventilation and decent shade.

A study published this week examined how passive cooling can mitigate overheating in housing situations that don’t typically allow renters to install their own air conditioning units.

Ample shade and natural ventilation can provide substantial relief during extreme heat events. But not everyone has access to them, especially not in multifamily dwellings, apartment buildings and other rented spaces.

Researchers found that edge-sealed blinds — which extend from edge to edge to create a snug fit with little to no light leaks — and box fans serve as an effective but accessible way to dramatically reduce indoor temperatures and improve air circulation.


Scientific models and floor plans for apartments in Portland and Seattle (among other cities), thought to be characteristic of rental units in both cities, were used to simulate indoor temperature under numerous scenarios. Building codes both new and old were also used to shed light on how these factors have changed over the years.

“Straightforward things like shading and ventilation might not sound particularly different than anything we’ve heard before,” said Alexandra Rempel, the study’s lead author and a professor in the environmental studies program at the University of Oregon. “The edge-sealing of the shades is really important and is not very well appreciated here.”

Last year from late June to early July, an unprecedented heat wave brought soaring temperatures to large swaths of western North America and British Columbia.

The ordeal lasted barely more than two weeks — less in some parts of the region — but it managed to trigger intense fires in Oregon and California, destroy crops, cause nearly $9 billion in damage, hospitalize hundreds and cause more than 1,000 deaths.

Washington reported 100 heat-related deaths between June 26 and July 2, according to the state, and experienced its highest temperature ever recorded.

In total, an estimated 1,400 excess deaths were caused by the heat wave last summer — more than 800 in Canada and about 600 in the United States.


“That’s just too many deaths,” said Mike Fowler, a co-author of the study and senior associate at Mithun, a design firm based in the Northwest.

During the crisis, public messaging at times encouraged people to seek air conditioning and open windows during the day. What people should have done instead, researchers found, is basically the opposite.

AC units can create a positive feedback loop as they take in and expel warm air, thereby contributing to a so-called urban heat island effect, whereas windows and blinds will better circulate cool air if they’re closed and drawn during the day when it’s hot outside, and left open at night.

“It becomes much, much cooler here at night,” Rempel said. During last year’s heat wave, temperatures dropped by 25 to 30 degrees every night in Vancouver, B.C., Seattle, Portland and Eugene, Oregon. “We can use that to our advantage.”

For residents without easy access to passive cooling strategies, Rempel urged landlords and building owners to provide assistance, and local governments to support those landlords and building owners. Doing so, she said, would help utilities prevent price hikes during the summer, and avoid the need to develop more sources of electricity.

Policy is beginning to catch up with these new realities. But, Fowler said, “where people are struggling is in existing buildings.”


Soon after last year’s Pacific Northwest heat wave, scientists found it was an incredibly rare event meant to happen once every 1,000 years, and that it was made 150 times more likely with climate change. All of the past seven years have been the hottest on record.

“Heat waves are the silent killers of climate change, but they don’t have to be,” Francesco Rocca, president of the International Federation of Red Cross and Red Crescent Societies, said during a briefing on June 14 to commemorate the IFRC’s inaugural global Heat Action Day.

Even now, extreme heat is terrorizing countries around the world as India, Pakistan, East Asia and southern Europe record life-threatening temperatures.

In May, Washington state climatologist Nick Bond said the chances of a historic heat wave happening again this year are remote. Still, while large amounts of precipitation during this unusually wet spring alleviated drought and wildfire risk, the Northwest remains dry, if not drier than usual.

“Most heat waves are forecast days or weeks in advance, giving ample time to act early and inform and protect the most vulnerable,” Rocca said. “The good news is that there are simple and low-cost actions authorities can take to prevent unnecessary deaths from heat.”