The move is in response to several years marked by thick smoke hanging over the city from summer wildfires, which officials and scientists have unequivocally connected to the slow-motion of the effects of climate change.

Seattle officials demonstrated the technology at one of the havens — a community center in the city’s Rainier Beach neighborhood — pointing out air sensors mounted on the wall, and describing how the building’s existing ventilation system had been retrofitted with special filters to keep it positively pressurized with clean air.

Along with the Rainier Beach facility, Seattle Mayor Jenny Durkan said at least two of the facilities could potentially be scaled up to shelter the city’s homeless population if air quality sinks far enough during the summer to endanger those unable to retreat indoors.

“We have to prepare as if this will be the new normal,” Durkan said, adding that 2018 saw 24 days with hazardous air quality levels due to wildfire smoke, including several reaching extreme levels.

That reflects a broader shift being felt across the American and Canadian West, and likely to continue in coming years, according to experts and federal data.

In 2017 and 2018, 15,625 and 13,750 square miles (40,469 and 35,612 square kilometers) burned in total in the US, mostly in western states, according to federal figures, compared to a 10-year average of 10,937 square miles (28,327 square kilometers) per year, while the fire seasons in British Columbia broke worst-in-history records both years.

That translated to a thick pall of smoke hanging over the region, well beyond Seattle, with Missoula, Montana, San Francisco, Spokane, Washington, and Portland, Oregon, all logging their worst air quality days on record in either 2017 or 2018, according to a recent study.

Although not as bad as in the worst years, including 2015, which saw Washington’s worst wildfire season in at least a century, the conditions are set this year again for a worse-than-average season.

At the Seattle event, officials described how that’s changing the character of the region, long known for its clean air and verdant landscapes.

“It’s a sad thing to say this, but if you love the outdoors, you might want to get out there while it’s safe,” said Craig Kenworthy, director of the Puget Sound Clean Air Agency.

Lynn Sereda, an area woman who attended the event, described being struck by the climate of the northwest when she moved from New Jersey in the 1990s.

“The first thing I noticed was how clean the air and water was here. I never though the air could be compromised,” Sereda said.

The first bad wildfire season she experienced, in 2017, was a departure from that.

“The minute I left my house you could smell the wildfire in the air,” Sereda said. “Honestly it was pretty frightening.”

Another attendee, Donna Funk, described a similar experience.

“I went out one day and there was ash falling from the sky,” Funk said. “I had never seen anything like that before.”