Washington Air Quality Forecast: Is Smoke Finally On The Way Out?

SEATTLE, WA — At long last, Washington may finally be getting the upper hand on a blanket of smoke that has smothered the state for nearly a week. Widespread relief could arrive by Saturday.

Forecasters expect a noticeable improvement to the air quality beginning Friday and gradually increasing into the weekend. While readings Friday morning were largely in the "unhealthy" range, some areas had improved to "moderate" and portions of the coast maintained "good" levels. An air quality alert will remain active for King, Pierce, Snohomish, Kitsap, Island, San Juan, Skagit and Whatcom counties until 10 a.m. Saturday.

Since a "super-massive" smoke plume poured into Washington on Sept. 11, sourced primarily from historic wildfires burning in Oregon and California, winds have continued to pull in new smoke to the region, often degrading air quality to hazardous levels in the Seattle area. Compromised air migrated north into Canada and east across Idaho, Montana and Wyoming. Hazy skies were reported as far away as New York and Washington, D.C.

The first shot at relief was quashed Monday after a weakened weather system failed to create the conditions needed to clear out the smoke, even as some rain showers arrived in Washington. This time around, forecasters are optimistic that rain showers Friday and Saturday, aided by west-northwest winds, will make a notable difference. Continued upper level winds are expected to prevent additional smoke from Sunday to at least mid-week. By Wednesday, another wet storm could arrive.

Clean air will not arrive all at once, but forecasts for King, Pierce and Snohomish counties show it improving to the "unhealthy for sensitive groups" range through Friday. The latest forecast map shows good air from the Olympia Peninsula down to Chehalis. In King County, the Puget Sound Clean Air Agency predicts moderate air by Saturday with good air by Sunday.

Live updates on air quality can be found via the Puget Sound Clean Air Agency, AirNow and Department of Ecology websites, along with the daily smoke forecast. New information will continue to be posted on the Washington Smoke Blog.

Why do air quality numbers differ between sources?

As many have likely noticed over the last few days, the readings shown on air quality maps can vary between apps. According to the Washington Smoke Blog, that is because of differences in how the state calculates the level of the health impact versus the federal government.

For example, readings on the Environmental Protection Agency's AirNow map will typically show lower figures than those reported on the state Department of Ecology's website. The federal number is based on the Air Quality Index, while the state values are based on the Washington Air Quality Advisory calculations — a more strict metric.

"EPA studies have assigned risk at a certain point, while Washington state toxicology research found more protective levels would better serve our community," wrote Odelle Hadley, a senior air monitoring specialist with the Olympic Region Clean Air Agency.

State officials said both calculations are equally trustworthy, differing only in how they measure the threshold for health effects.

How did this smoke event compare to previous years?

Dr. Beth Friedman, a scientist with the Department of Ecology, ran calculations earlier in the week analyzing how 2020's smoke stacks up to recent years, including 2018, when ash and smoke from wildfires in British Columbia descended on Western Washington.

Friedman found Washington has spent fewer days breathing harmful air than in 2017 and 2018, but the air we have been exposed to in recent days is markedly worse than previous smoke events.

"We had a late start to wildfire season this year," Friedman wrote. "However, the amount of time we have spent breathing Hazardous air is unprecedented. Even if we look as far back as 2006, we don't see Hazardous conditions occurring anywhere as long."

The analysis also examined which areas of the state were hit hardest by smoke in September. Friedman found southern Yakima County and parts of Okanogan County had the most polluted days, while some of the worst air was in the Columbia River Gorge and Clark County.