August 15, 2018

Seattle's Worst 24h Air Quality on Record

Air quality in western Washington is very poor right now.

Incredibly, in central Puget Sound it is probably the worst in the nearly two-decade observing record of the Puget Sound Clean Air Agency for any time of the year.

I have been here a long time and I have never seen anything this bad.  The view from the Seattle SpaceNeedle Panocam is murky (see below)

And the view from my department is very mountains and can't even see across the Lake.

But now, let me really impress (or depress) you.  Below is a plot of 24-h average particulate concentration (PM2.5) in the atmosphere at the Puget Sound Clean Air Agency Duwamish site in Seattle.  The past 24-h was the worst on record for any time of the year.  Number two was the smoky period last summer. 

Historically, Seattle has its worst air in the winter from wood smoke and other combustion products, but today and last year were summer maxima from wildfires--very different animals.

The observing site in Tacoma also had its record in the past 24-h hours.

So why did our near surface air quality get so bad so fast?  

Fires were burning for quite a few weeks in British Columbia, California and eastern Washington, but western Washington had clean air at low levels (off the Pacific) with smoke aloft.  But on Monday, surface high pressure started to build in north and east of us (see map), resulting in easterly and northeasterly flow over the Cascades that brought the smoke over and down the terrain into western WA--allowing smoke to get to the surface.

Surface map at 8 PM Monday
I ran some low-level air trajectories ending in Seattle at 11 PM Tuesday night (using the NOAA Hysplit system).  Air ending at 100 meters above the city came from smoky BC, while air at 1000 meters were from eastern WA--both sources of smoke.

High pressure aloft amplified just offshore, resulting in strong downward motions in the lower atmosphere, which produced a subsidence inversion from the surface up to about 3000 ft.   The inversion (temperature increasing with height) was very obvious in the balloon soundings at Quillayute, on the WA coast, and from the Seattle profiler (see below).  Inversions act as atmospheric lids, preventing the smoke from mixing out during the day.

In short, we had the "perfect storm" for wildfire smoke around western Washington.  Lots of fires around us, a meteorological situation that pushed the smoke to low levels, and the development of an inversion that kept the smoke in place. 

As I write this (10 AM), the air quality  in Seattle is getting even worse (see plot)

EPA's AIRNOW site provides the five worst air quality locations in the U.S. each day.  Well, today the Northwest possess ALL FIVE of these sites:

Chelan has a startling value of 211, with the rest right behind.

Incredibly, historically bad air and unhealthy for all.  No running for me today.  Expect very slow improvement on Thursday.


  1. Out in Forks, my smoke alarm kept going off. That never happens unless I'm trying to cook something.

  2. yesterday WA had all 5 of the Highest 5 on AirNow, a dubious honor as the Highes 5 are the places with the worst air quality IN THE COUNTRY. Wenatchee took top honors as the worst. But it was, as Cliff noted pretty awful on this side of the mountains too.

  3. Cliff, I'm not able to see it on the forecasting sites yet - but have you seen any signs beyond Thursday for the smoke blowing out yet?

  4. Glad I live in Cleveland where the air is clean these days. Right now I am sitting out in the yard in comfortable temperatures and enjoying summer life. It is not all perfect, though. As I write this I am observing one of the large marauding herds of urban deer which are almost as bad as forest fires. These deer are the size of heifers, eat everything, and are not about to go back to the nearby forest where they would have to work a lot harder for their food. The only vegetation left in the forest is trees that are too big for the deer to eat. Seattle may have dirty air, but at least you don't have marauding herds of urban deer.

    1. Yes. Deer are equivalent to wild fire smoke that is a serious health threat to kids, elderly and those with health conditions.

  5. Thank you for going to trouble of gathering the information, and presenting it so clearly. I'd hoped to go out on Lake Washington today with a friend, but now I think not.

    David Summers

  6. Why is this not taking into account historical data from PSCAA?

  7. I've lived in the Seattle area for 25+ years, and never experienced smoke events as bad as this year and 2017. The data you quote seem to agree with my memory!

    A previous blog explained that there aren't, in fact, more/larger fires in recent years compared to historical norms (at least in CA).

    What do you think accounts for the recent worsening of the smoke situation? More fires in BC? Change in weather patterns? Random variability/too early to tell?

    1. Globally there aren't more fires, but up here in BC we have seen a major uptick in fires since the 1990s. 2017 was the worst year on record, and 2018 is already the 2nd worst year since 1958. Here is a map I created showing the long term trend...

  8. Not seeing the ash fall of last summer here in north Whatcom County, and yet the air quality seems worse. Very dense and definitely disaffecting. This is the first time in my life as a Western Washingtonian that I've suffered from air quality. Pretty depressing.

    (Btw, Charles, I was out your way recently and it was definitely greener, and the air cleaner. But rest assured this region has plenty of "marauding urban deer".)

  9. Mention is made of wildfires burning in "British Columbia, California and eastern Washington" but not Oregon. Most of the highest AQIs in the country are in Southern Oregon and all the smoke down here comes from local fires. We are in a truly apocalyptic situation down here in the Rogue Valley.

  10. I haven't breathed air this bad since growing up in New Jersey in the 1960s. :-(

  11. I'm remembering the 60s and the 80s and I say no way for the worst at anytime of year. Not even close to winter inversions in the bad air days of before Cliff Mass.

  12. Port Angeles hovered around 240 much of Weds. I discovered I'm in a sensitive group.

  13. Great blog post and really interesting to see this year and last compared to the last 20 or so. Yeah, it was really bad back in the late 80's and early 90's when you could only see downtown from the Safeco tower through a thick haze (I had a window office on the 18 floor), but our air has been so much cleaner over most of the last 20 years. Air is better this morning here (Thursday) near Fauntleroy , but the smoke is still up above us here.

    Another good resource for more localized air quality is the map. Like PWS, it is personal air monitoring equipment that is a bit more scattered around. I look at it and PSCAA maps to get a better overall picture. I may have to add one to my PWS station if this is going to be a yearly thing for us now.

  14. Having grown up in the Willamette Valley during the era of grass seed field burning, I'd say that was worse:
    also, see "Black Tuesday", 8/9/1969.

    But it's pretty bad these last two summers...

  15. Cliff I love your blog, I moved from Seattle to Phoenix but I still observe your blog out of curiosity... Is there a Cliff Mass counterpart in Phoenix area that has a detailed blog like you?

  16. I've never seen so much smoke hovering around my place NE of Arlington, WA. I drove 27 miles up to Darrington, WA yesterday thinking it might be better at a higher elevation. Boy, was I wrong! Darrington surrounded by the Cascades, and at the foot of Whitehorse Mountain was a smoke bowl. Smoke so thick that I could not even see Whitehorse Mountain that looms above the town. I am sensitive to this smoke, but how can you stay indoors for this long? Impossible!

  17. We just spent the past week in the San Juan islands where it’s smoky, but NOTHING like seattle. As soon as we came into the city I started feeling sick (I’m not in good health) coughing, horrible migraines, eyes hurting, and nausea. Not sure if anyone else is experiencing these symptoms... I’ve lived in Seattle my entire life and have never seen anything like the skyline (or lack thereof) before.

  18. You have to remember that we are coming out of several decades of air quality improvement, thanks to the EPA. I remember visiting LA in the 1960's and the air was yellow and thick with unburned hydrocarbons and tetraethyl lead. The highways smelled like a chemical factory and made me sick. It was scary, and it was like that a lot of the time.

    But the focus on improving air quality, driven most of the time by both political parties, is now giving way to partisan politics where one party believes we've made everything too clean, at too high a cost.

    So between AGW catching up with us and a deliberate attempt to degrade the air quality protections we've enjoyed, the clock is potentially going to be turned partially backward.

    While smoke from forest fires is no way as bad as that lead-saturated hydrocarbon stew from unburned gasoline and too many cars, and the causes are very different. we are for the first time in real danger of going back to a less clean and less healthy past.

    This wood smoke is just a wake-up call that other kinds of pollutants could also increase if we rolled back regulations. What is bizarre that right when we are on the threshold of renewable energy dominance and electric cars, the government decides to turn back.

    I swear some people have a self-destructive gene. Sort of like being one knock-out blow away from winning a war, and then deciding to heck with it and going home.

  19. Cliff-

    I was looking at the radar this morning and am seeing precipitation showing up east of the cascades from Quincy and Wenatchee north up to Omak and also down in southeast Washington, some of it heavy(oranges and even reds). There is absolutely nothing in the forecast about this. Is there any chance the smoke is causing the radar to think there is precipitation? Thanks for your time!

  20. lol ppl still askin questions like they gonna get an answer. Liberals. Smh


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