August 24, 2023

Regional Wildfires Were Greatly Reduced by Recent Rain

 For those of you concerned about wildfires and wildfire smoke, I have some very good news:  recent rain has greatly knocked back regional wildfires, particularly in British Columbia and Idaho.

Furthermore, substantial rain is predicted over British Columbia next week, which should help maintain the reduction.

To illustrate the changes, below are NASA MODIS satellite images taken around noon today and on August 18th.  On August 18, major fires were pushing lots of smoke out over southern BC and the north Cascades.   MUCH less smoke today, although a thin veil of regional smoke remains.

August 18

August 24

Idaho and western Montana imagery are shown below. On August 18th, there were major smokers over the Rockies.

But only some residual smoke today!  Much better.

The main cause of this reduction was the substantial rain during the past week.  

Below are the totals over the past five days.  1-2.5 inches over portions of southwest BC and Western Alberta.   And similar totals over Idaho and western Montana.   Serious precipitation.

You can thank the remnants of Hurricane Hilary for a lot of this wet bounty.

And more is coming.

For the next few days it will be generally dry and warm, but early next week the spigot will be turned on again as a strong trough of of low pressure moves through. Take a look at the predicted totals for the 48 hr ending 5 AM next Thursday (below).

Wow...southern BC will get a lot more rain and that will further extinguish or reduce wildfires.   The main source of our recent smoke will be greatly lessened.

The northern Rockies and Cascades will get precipitation as well

At this point, I am increasingly optimistic that the current lower-than normal burned acreage situation in Washington State will continue into early September.  The amount of forest fires has been particularly low over Washington State this summer.

Keep in mind that we only have about a month left of the Northwest wildfire season.


  1. Back to the way things were in the '80s and '90s, you'd be guaranteed to get some sort of rainstorm before Labor Day!

    1. The trees and bushes at the edge of where I live, some with yellowing leaves (and leaf fall starting in early July here), badly need rain, and I hope it comes soon. When the Sourdough fire began, I thought, that's really not close, but on the other hand it's too close, considering how fast fires can roar out of control. Rain, and lots of it. Summer is over.

  2. Each of the last several mornings, I've looked at how wet the dew has made the grass in my lawn, and take a good amount of satisfaction in the effect that should have on the 1-10 hour fuels around these fires.

    I know they can still burn as nearby flames dry it out, and especially as it dries during the day, but it really helps give a sense how mild temperatures and humid air help tame a fire.

  3. The rain missed me and I missed the rain. Further, the NWS thinks KELN will get to 93° on Monday – then maybe rain.

    Was there a cloud burst in Prosser? 1.31" on the precip map appears there with almost nothing else.

  4. Thank you! local news reports smoke over this weekend but did not go on to explain if it was vertical, ground or at what level. Thanks for your post

  5. Fire acreage may be down this year but according to the DNR the number of fires in Washington this year is about twice that of last year. We have been lucky so far in that there have been no significant dry lightning outbreaks in Eastern Washington which usually results in our larger forest fires. As with last summer, the main area of lightning caused fires was near and west of the northern Cascade crest in a location not usually prone to large fires.

  6. It's going to be quite hot here in Portland over the next few days, but we did receive about an hour of thunderstorm activity early this morning, coupled with some rain. Nothing to write home about, but every little bit helps at this time of year.

  7. Can't recall when we last saw rain here in north Whatcom County, and the smoke today is pretty unbearable.

    1. Did not get a drop in northern Skagit county on the 22nd and 23rd, in Bellingham it down poured.

  8. Nice rain yesterday in South Sound, smoke and 90s today.

  9. Hi Cliff, perhaps you have already commented on this in the past but could you provide a recommendation for how to interpret Purple Air pm2.5 data?

    Currently, I've been using the US EPA PM2.5 AQI data layer coupled with the US EPA conversion... which yields a particular interpretation that often differs from AirNow's delayed numbers. What do you like to use? In a past graphic you shared, it looked like you had selected raw pm2.5 with the LRAPA conversion, but perhaps I misread that.

    Thanks for your commitment to unbiased reporting!


  10. Great post Cliff! As expected from a great scientist like your self. I've learned much from you.

  11. For those that are wondering, First off, I grew up in this area, and recall years where we get some rain in August, usually a bit at some point in the middle of the month, but can remain between upper 70's to mid 80's, but the extreme hot weather has normally passed us by, by early August, but not always and can remain dry and warm through much of Sept.

    I recall in the past the Puyallup Fair (now the Washington State Fair) would be rainy some years, cool and nippy, but dry other years, or bordering on hot during the day still other years. and this being in September.

    On average, the rains slowly begin in mid to late Sept and often by October, it's officially on.

    I do distinctly recall one year, 2012, when we didn't get any significant rain until late October and it remained dry and dusty well until then, and warm through at least Sept. That was because our summer didn't start until mid to late July that year. That is not all to common, but it does happen. Also, our blackberries were late to ripen and were still ripening in September.


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