Washington Smoke Map

*The map above is not able to display all state air quality monitors. Click here to see all monitors in Washington: WA Ecology Air Monitors

Note: Some users might notice intermittent discrepancies in colors shown on the map of air quality monitors above, and those reported on the Department of Ecology's official page. This is because Ecology believes their method of calculating the air quality category (i.e. “Good”, “Moderate”, Unhealthy” etc) is more protective of public health in Washington. If in doubt as to which better represents public health risk, use the more stringent of the two (i.e. the map showing worse air quality).

Wednesday, September 6, 2017

Forecast: smoky with a chance of ashfalls

There was hardly a corner of the state that wasn't battered and bruised by smoke and ash yesterday. The smoke layer reduced maximum solar radiation intensity by almost 50% in Seattle, as seen in the following plot. Compare 1 and 2 Sept (sunny days in western WA) with 5 Sept.

Further, Ecology's air quality monitoring data website and the map of monitors above were feeling the strain of increased web traffic. Staff have been working overtime to restore and maintain services. If all else fails, EPA's AirNow site can serve as a backup.

Compare air quality yesterday (WA, OR and MT smoke) with a BC smoke episode last month
Colored dots are air quality conditions, with darker colors representing worse air. Satellite pictures were taken around 1:30PM. Spokane area air was bordering hazardous all day yesterday.

When will it all go away?
Tomorrow for western WA. Not fast enough or complete enough for eastern WA.
  • Western WA: Marine air starts to push in slowly this evening and it will be Thursday before western WA is able to flush out. Expect ash to stop falling by tomorrow.

  • Eastern WA: The Montana smoke tap will be turned off by Thursday, so most of central and far eastern WA will "improve" from Hazardous/ Very Unhealthy to Unhealthy/ Unhealthy for Sensitive Groups. It will be well into Friday before further improvements ripple through, but most areas will be downwind of fires in and around the Cascades, so Good air quality isn't on the immediate horizon.

How long will it STAY clean?
Not long enough, it seems.

Airflow turns westerly after the flushing tomorrow. Few of the smoke models seem to be capturing the large pall of smoke hovering over the Pacific ocean.

Some of that smoke is likely to mix down into western WA on occasion but don't expect air to be much worse than Moderate in a few spots. Problem is that models are building another ridge of high pressure (= light winds and poor smoke dispersion) from Sunday- Tuesday. Don't yet know if east winds which brought smoke from the Cascades to western WA will be part of the calculus or not. Please stay tuned.

Finally, about the  ash
Many questions were raised about the toxicity of ash. Our toxicologist Dr Matt Kadlec confirmed that ash from forest matter is basic (pH ~ 9) and does contain heavy metals and PAHs. It can cause skin/ eye irritation. However these particles are far too large to be inhaled and fine particle pollution measured by air quality monitors are a far more serious health concern. Besides, ash has not and will not accumulate in sufficient depths in our cities to put people at risk when cleaning it up.


  1. Can you please explain your new AQI system. It used to be that you gave an single simple AQI value per location (dot). For some reason you stopped doing do. Instead we get a cryptic readout of values/averages for PM2.5 (but not PM10 or Ozone). Even these PM2.5 values don't make sense (to me). E.g. PM2.5 has been listed at 29 ( a green value) but the dot for the location is yellow (indicating a value > than 50.) This is a great web site but to be useful to ordinary non-geeks the information has to be clear.

    1. This is a repeat of a post by Ranil Dhammapala of WA Ecology. It should answer your questions: There are multiple considerations in displaying air quality data: which pollutant(s) to show, how colors are determined and how can one pull up historical data for a given site.

      Since this is a blog about smoke, PM2.5 is the most important pollutant (others do feature but not as prominently. The bulk of PM10 in smoke consists of PM2.5).

      Colors arent driven by the last hour's reading alone. You seem to have mistaken NowCast values for AQIs. The NowCast method is an EPA algorithm that downweights older data and gives more prominence to more recent data. It is *approximately* similar to a 3-hr running average although the algorithm is more complex. The NowCast method was adopted a few years ago to make the AQI more responsive to rapid changes in air quality, and applies to PM2.5, PM10 and O3.

      So a NowCast value of 22 means the ~3hr running average of PM2.5 is 22 micrograms per cubic meter. This is well within the Yellow category according to EPA's Air Quality Index, which transitions from Green to Yellow at 12, Yellow to Orange at 35... etc.

      All the epidemiological research shows, that health effects are continuous, not stair stepped, with AQI. There might not be much difference in health conditions experienced at AQIs of 99 (Moderate) vs 101 (USG).

      So while a multipollutant based single AQI value on a continuous color scale would be most informative and protective of public health, I dont believe EPA or Ecology are at a point where we can iron out all the kinks and roll out something uniform just yet. I believe the Canadians have (or are considering) such a scheme and we too are actively discussing improvements to displaying AQ data. But even with that, sensitive individuals will need to self-adjust AQIs according to their health conditions and take necessary steps.

    2. Thank you for the explanation. However, I just checked the EPA AQI for PM2.5 pollution and it still uses the 50-100-150... quality transitions. (https://airnow.gov/index.cfm?action=particle_health.index) I have been unable to find any table for PM2.5 that transitions from "12 to 35...etc. Given that your blog is about smoke, as you say, maybe it would be helpful to post what the thresholds are for particulate matter. I get that for PM2.5 G<12, Y<35 what is orange, red, and purple?

    3. We have desisted from publishing this because it has led to much confusion. Calculations arent straightforward and explanations are technical. Anyway FWIW EPA AQI breakpoints are at https://en.wikipedia.org/wiki/Air_quality_index#Computing_the_AQI. Bear in mind that these transitions apply to the NowCast concentrations, not the hourly concs.

  2. Do you consider Central Washington (Ellensburg) to be part of Eastern Washington in these analyses?
    Thanks for all the work you all are doing on this!

    1. Yes, same general forecast applies east of the Cascades

  3. So will Seattle be clear over Friday/weekend?

  4. Please see the latest smoke forecast under the “Home” tab on this website. That tab is under the air quality map on the left. Scroll down until you see it. Check back for forecasts during the week.


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