May 09, 2019

Will Puget Sound Experience Another "Smokestorm" This Summer?

One of the most frequent questions sent my way during the past month is about smoke this summer.

Will Puget Sound country have another major smoke episode, as we had during the Augusts of 2017 and 2018?
                                  Picture by Bruce Englehardt under Creative Commons License

Several media outlets are already talking about an above-normal wildfire summer for our region (see below), based in part on the below-normal snowpack in the north Cascades, the warm/dry conditions of the past few weeks, and heat wave in late March that resulted in dozens of small fires in western Washington.  Some are warning about more dense smoke.

My take?   I believe that although it could happen, it is most probable that we will escape the dense low-level smoke of last summer.

To put things into perspective, below is the daily maximum small particle (PM2.5) concentrations during summer since 1990, produced by Erik Saganic of the Puget Sound Clean Air Agency.  An IMPROVING trend from 1990 through 2016, which might expected from cleaner cars and trucks, as well as other technological improvements.    But then we have had two extraordinarily bad summers in a row--I mean in a different world from the previous decades.

Is this the new normal?  Caused by global warming?  Should we expect the trend to continue this year, resulting in the worst air quality of any major world city, as occurred last August? (see plot).

I think this is unlikely.    I believe we were very unlucky last year with fires and winds happening to align to inundate Seattle with dense smoke.  Global warming is a long-term trend.  Why would a downward trend be followed by a spike two years in a row, if global warming was the main driver?

Let's start with an interesting question.  Do more regional wildfires mean more dense low-level smoke in Seattle?

Here are some figures from a previous blog of the area burned over Washington State from 1992 through 2017.   It really correlates poorly with smoke levels over Puget Sound.  There was a BIG, BIG spike of wildfire area in 2015 (a very warm, dry spring/summer that year), but only a slight increase in the worst smoke day here in Seattle.   Much less area burned in 2017, but much more smoke.  The correlation between wildfire area (or total number of fires) is poor.

The truth is that most of the smoke from British Columbia, eastern Washington, and Oregon doesn't get to us at low levels for some basic meteorological reasons, including the blocking effects of the Cascades and the typical onshore flow into western Washington.  And to get really smoky in Seattle, the fires have be close...either in western WA or in the nearby Cascades immediately upstream of us.

Even during the last two "smoky: summers, MOST of the time our low-level air quality was fine, with the long-distance smoke staying aloft.   If you doubt this, here is a plot from the wonderful Puget Sound Clean Air Agency site showing you the maximum 24h small particle concentrations last summer.  Most of the summer had decent air quality, with the exception in mid-August.   August 21st was the worst day.

What happened?   A "perfect-smokestorm" with an unusual set up.   Fires really close to us in the north Cascades and strong easterly winds from the perfect direction to inundate Puget Sound with smoke (see image).

Very unusual.  You need major fires in just the right location (the north Cascades), plus the perfect configuration of winds (northeasterly and easterly flow), to get the smoke levels of last summer.

The forecast for 11 AM on Monday August 20th at 850 hPa (about 5000 ft) shows the  configuration, with trough of lower heights centered to our southeast, with an extension over NW Washington. 

What about the 2017 smoke season? As shown below, the worst smoke was limited to about a week in early August, with August 3-5th being the worst.

Why so bad then?  Fires to the northeast of Seattle with simultaneous strong northeasterly flow (see satellite image from August 5th).

I believe that we were unlucky two years in a row, and the unusual nature of the combination is shown by the lack of such events in the previous decades, even with similar numbers of fires and even greater fire area (such as in 2015)

The question is not whether there will be wildfires in the region.  There will be, particularly with our overgrown, poorly managed eastside forests and increasing human habitation and activity in them.  The question is whether the perfect conditions will occur a third year in a row to push a dense plume over Seattle.

Yes, we might get two sixes on the local atmospheric dice for a third year...but I suspect the odds are against it.


  1. I think this under reports the impacts during the last couple of years. For example, the jolly mountain fire was still going in September 2017. "We" might live in Seattle, but the entire Cascades are our home and smoke will affect us even if it is 2000 feet aloft.

  2. Thanks for your work, which I highly respect.

    What would have to happen for you to acknowledge that we may in fact be witnessing the start of an exponential move up in fire frequency and related aqi effects? I have a phd in math - parabolic growth isn't as statistically uncommon as many assume. Look at long term financial charts on a logarithmic scale (bitcoin in 2015, gold in 2000, sp500 in the early 80s before Reagan's SEC legalized corporate share buybacks).

    My family and I had to evacuate our home in Roslyn last summer - the situation is a bit more dismal than the picture you portray, in my humble opinion.

  3. I hope you are right.

    A third year will push me over the line and install a full HVAC system in my house.

  4. So basically, it's not the fire, it's the wind. Then the media gets it completely wrong and sends out false information (on purpose, of course). It's funny what some folks do to make a living.

  5. Regression to the mean will be ‘working’ to return our summer back to normal. Hopefully. Seems to be working on the Mariners now.

  6. Cliff
    Both summers, the smoke in Seattle came mainly from British Columbia, so why are you only looking for correlations with fires in Washington??

    From Wikipedia,
    “By September 12, there were 158 fires burning throughout the province.[5] A total of 12,161 square kilometres had burned by the end of the 2017 fire season, the largest total area burnt in a fire season in recorded history (1.3% of BC total area).[6] This record was broken the following year, with five of BC's worst 10 fire seasons occurring since 2010.[6] However, the 2017 fire season was also notable for the largest number of total evacuees in a fire season (65,000 people), as well as for the largest single fire ever in British Columbia.[7]”

  7. Thank you, Cliff.

    I've been wondering about all the wildlife in the areas with large fires but haven't come across any information on the subject. So I began searching for it. OPB (Oregon Public Broadcasting) has a good article written by Aaron Scott on Oct. 5, 2018. Perhaps some people would like to read it. There may be more information out there. Here's the link...and hope it works

  8. We have had several small fires already in north central WA all caused by people burning brush and woody debris in their yards when it was very windy. Wild land fires start with lightening strikes (2018 McLeod and Crescent fires) and by humans (Diamond Creek fire 2017-unattended or not totally put out campfire; Rising Eagle fire 2017-broken tail pipe dragging on pavement caused sparks), and are pushed by wind. If the carelessness, ignorance and stupidity of humans could somehow be curtailed, we'd be in better shape! Glad to see the Okanogan/Wenatchee Forest Service thinning and conducting prescribed burning this spring in the national forests. We need fire for forest health and to reduce the build up of fuels from previous decades of fire suppression.

  9. We have a lot of catching up to do....

    “Florida leads the way, burning more than 2 million acres last year. Arizona and New Mexico set intentional fires on just over 570,000 acres in 2017, while Oregon, Montana, Idaho, and Colorado joined California in burning a combined 169,000 acres.”

    ......considering Washington alone has 22 million acres of forest.

    Great article on prescribed burns:

  10. Cliff, I thought you might also touch on the fact the USFS has initiated a number of prescribed burns this spring (see Pine's comment above) in Central WA (Wenatchee Valley, Ingalls Creek, Cle Elum, Blewett, etc). I am hoping the shift is finally taking place to: 1) significant prescribed burns in the shoulder seasons and 2) putting out fires asap between June and September (like was the USFS priority until the shift to “managed burn” in the 90’s, which exploded the number of acres burned in the summer - and the amount of smoke in the air, particularly in E. WA in the last 2 decades).

    They already started shoulder season burning last fall (it was successful) and this spring has been significant as well. Yes there have been complaints ( but if our goal is to actually bring the forests back to health without it turning into tragedy in August, I support this.

    Clearly the “put it out at all costs” strategy of the mid-20th century hurt our forests. But any comparisons to “acres burned” today versus the last century (as has been reported constantly in recent years) is ridiculous due to the radically different ways wildland fire was/is managed. My hope is we get back to a more rational approach, and what we are seeing today gives me hope.

    We have a long ways to go though.

  11. I agree with your overall assessment. I do take some umbrage with the idea of correlating total acres burned with likeliness of smoke or any correlation with global warming. Far more important is where the fires are located. That and likeliness is the true impact of global warming on wildland fire.


    Hilary Franz, state commissioner of public lands, had a recent discussion with the Seattle Times about the current fire season

  13. Max temp in NW Bellingham today 83.4F

  14. Get over it. We live in and or around forests. Sometimes they burn.

  15. Much of the smoke the last 2 seasons were from fires in British Columbia and much of the Cariboo-Chilcotin region of the province had burned over the past few years. The fuel remaining to burn is significantly less than it was even 2 years ago. At least it's the case in that region about 300 miles to our northwest and a region that has been hit hard with the mountain pine beetle meaning more dead tress and deadfall which has also contributed to the fuel problem. Also we often get smoke drifting down from that region due to NW flow that brings the smoke right into the lower Mainland and Puget Sound. However, there isn't much left to burn in that region at least not huge swaths of forest that can lead to massive fires. So fires in that region should be less of a factor regarding smoke down here.

  16. yes it's wise when talking about the "pacific Northwest" to include the majority of the Pacific Northwest.

  17. There wouldn't be a smoke problem without fire, and it takes fuel and spark to ignite Forest fires. Weather may provide spark in the form of lightning, but we'll managed forests do not become tinder overnight. I live surrounded by forest, and lack of good forest management worries me far more than Pacific Northwest seasonal dry spells do.

    When the Mt Baker Snoqualmie was logged, we had resident fire crews, maintained roads, and fewer stands of snags ("dead dry trees"). Policy has changed, here and to the east. Small wonder that there's more fire, and smoke.

  18. Will the sun rise tomorrow? I believe it could happen.

  19. Putting aside smoke drifting to Seattle for a second. How strong is the correlation between low snow years (like this one) and big fire years? It is pretty easy to see how much of Washington State burned (Wikipedia has a nice chart ( Finding year by year data on snowpack is more difficult. I've seen some charts on sites like Twitter ( but I find them difficult to read (I can't tell which year is which). It would be nice to see a chart with (at least) three columns: Year, amount of acreage burned, snowpack as % of normal on April 15. I'm not sure the correspondence is as strong as people assume. I think the particulars in terms of weather(especially in August) matter a lot more. A big storm with lots of lightening followed by hot, dry and windy weather is bound to cause a lot of problems, no matter how much snow fell the winter before.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

More Wildfire Misinformation at the Seattle Times

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