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caption: Kathalina Hoffman, left, and Brian Muoneke, right, look toward downtown Seattle as a massive plume of smoke from wildfires burning in California and Oregon made it's way into the area on Friday, September 11, 2020, at Kerry Park in Seattle.
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Kathalina Hoffman, left, and Brian Muoneke, right, look toward downtown Seattle as a massive plume of smoke from wildfires burning in California and Oregon made it's way into the area on Friday, September 11, 2020, at Kerry Park in Seattle.
Credit: KUOW Photo/Megan Farmer

Why western Washington air doesn't smell so smoky anymore (but is still harmful)

The air in the Puget Sound region remains unhealthy because of wildfires, but it doesn't smell as smoky as it did last week.

That's because something has changed.

The smoke we're breathing around western Washington, days after it arrived, is kind of old.

"When the smoke was fresh, you know it's basically like standing next to a campfire, you're getting all of those fresh emissions right off of the trees," said Farren Herron-Thorpe with the Washington State Department of Ecology. "And then, as it sticks around and lingers in the atmosphere, it starts to chemically react. It mixes with water. So it doesn't smell the same."

The color of the sky has changed as well. It's whiter, instead of the orange hue that tinted the daylight when the smoke first showed up.

Herron-Thorpe says that is because of a combination of factors. It's partially because of cloud cover. And it's also because most of the smoke is close to the ground -- not high above us, where it would change which colors of light reach the surface.

Unhealthy air from wildfire smoke is going to stick around the Puget Sound area at least through Wednesday. But it could take a little longer to clear fully out the smoke around Puget Sound.

"There is a storm system that’s moving in from the West — so, out over the ocean — and that’s coming in, bringing winds, and it looks like it’s going to reach the land sometime Thursday/Friday," said Graeme Carvlin with the Puget Sound Clean Air Agency. "And then hopefully that will break that smoke persistence that we’re seeing here.

Climate and wildfire smoke

Winds from the east brought much of the smoke we're seeing in western Washington right now. But is that the result of long-term changes in the climate?

Crystal Raymond is studying that question along with her colleagues at the University of Washington's Climate Impacts Group.

"The climate is setting the stage to get smoky conditions when we do have those winds," Raymond said. "We've had very dry conditions and those dry conditions persisted into early September. We've had some record hot temperatures in early September which really just kept the fire season going."

The first plume of smoke last week blew out of eastern Washington where wildfires continue to burn. A second round of smoke came from neighboring states to the south. Easterly winds down in California and Oregon blew smoke out over the Pacific Ocean. That smoke then made a right turn and came over to Washington.

Seattle has one 24-hour smoke shelter that will be open at least through Tuesday morning. The city has suspended free outdoor Covid testing, and library services are reduced due to the smoke. Seattle’s parks are still closed through Tuesday.