Thursday, September 16, 2021

Most smoke-impacted areas in Washington during summer 2021

As we await potentially season ending rains this weekend, this may well be our last post for summer 2021. So we focus on the two areas most impacted by smoke in summer 2021: portions of Yakima and Okanogan counties.

Fires in the Methow Valley led to poor air quality in Okanogan county earlier in the season than in previous years. The Schneider Springs fire in western Yakima county has been causing trouble since August 4. Here's a plot of all monitors in each area averaged together on a daily basis. We've included low-cost PurpleAir sensor data by adjusting them with the same correction factor as in the map above. 

To visualize the summer average of PM2.5 in each of the communities, we constructed an interactive map by fusing satellite data, air quality model data and all available monitoring data. We used the same monitors as above, but only included PurpleAir sensors which reported at least one month of data. More geeky details are available on request.

Click on the image below to view the interactive version. 

Disclaimer: this map is for informational purposes only. It does not establish legal culpability nor should it be used to distinguish air quality differences between your front yard and back yard. 

You can see where the most impacted areas were: right by the fires and all the higher terrain where plumes hit, followed by nearby valleys where smoke drains into. Since these are approximately 3-month averages, they're not directly comparable against the daily and annual federal PM2.5 standards of 35 and 12µg/m³ respectively. 

Not to trivialize smoke that plagued other parts of the state, but the sad reality people in these two areas faced was worse. 


  1. 'Season ending rains' are three words that are music to my ears. As much as I enjoy and appreciate your blog, glad I didn't have to check it multiple times a day, like I last September (I live in Seattle). Thanks for the valuable information and the helpful visuals though - here's to an end to the 2021 fire season (at least in the PNW).

  2. I was awakened this morning about 5am by strong acrid smoke entering my First Hill/Capitol Hill apt. in Seattle -- had to close all the windows. The smoke seems still present at 6.45 when I open windows, but local news reports nothing and the weather app says air quality is good. Any idea what might be happening? Btw, no sirens or other indications of some nearby building fire as an explanation.

    1. Hi Anonymous, currently all of the air quality monitors near the area show GOOD, so whatever it was has mostly dispersed. Several of the privately owned Purple Air monitors in First Hill/Belltown/South Lake Union did show a spike starting at about 3:30, and reaching MODERATE air quality, and dispersing within an hour or two. It was first detected in Belltown, and so may have drifted east and northeast from something docked or in the water... just a guess. We don't have any further information or reports at this time as to what it was. And, I don't see anything on Seattle 911/Fire that fits this time and location. So, it's a still a mystery.

  3. Thanks for your excellent work here. Noting that the link to the interactive map is broken - 404 / not found.

    1. Apparently a couple servers at x10host went down for nearly a week. Looks like it's all back up and running now.


We monitor this site during business hours, Monday through Friday, 8AM to 5PM. We encourage your questions, comments, and feedback. We ask that everyone be respectful of the opinions of others, and avoid comments that are defamatory, inappropriate or off-topic. If you have an emergency, please call 911.

We moderate all comments to prevent spam. Your comment will publish upon review