September is here!  September 1 marks the beginning of meteorological fall in the Northern Hemisphere.  Of course, that’s not exactly how Pacific Northwest weather works.  In reality, early-mid September often feels like a blend of summer and autumn:  days are still warm and sunny, but nights are beginning to get cooler.  This morning sure exemplified that narrative:  the (not so accurate) app on my phone showed a temperature of 48 degrees this morning in my Orchards neighborhood.  Some spots along the northern Oregon coast even dipped into the upper 30s!

We still have one more bout of hot weather to get through tomorrow Friday through Sunday, before cooler conditions appear to settle in for good.  But first, let’s look back at meteorological summer, which includes all of June, July and August.

SUMMER 2022

It was another hot one!  That much is obvious:  Portland Airport racked up 26 days 90+ by the end of August, and since then that total has ticked up to 28.  The all-time record is 31 days set in 2017.  We probably won’t break the record this year, but we could flirt with tying it.

We also had the hottest August and the hottest calendar month on record, at 75.1 degrees F.  That’s actually hotter than the “old” August normal temperature for The Dalles!  July was the 4th hottest July, at 73.7* F.  We had almost no days with a high temp below 80* from mid-July through the end of August.  That’s quite a far cry from a ‘traditional’ Portland/Vancouver summer, when we saw regular periods of marine clouds and temps in the 70s almost every season.  Instead, it feels almost exactly like a classic Mediterranean climate now.

Let’s look at the charts for the summer.  First, June-August at PDX:

 

It was the 3rd hottest summer on record, ranking about one degree behind 2015 and 2021.  Both those summers were buoyed by unusually hot Junes; remember the 116-degree heat dome last year???  But July and August are normally our two “core” summer months.  Let’s look at just the July-August period:

Wow, we blew the old record away by 1.3* F!  In short, we’ve never experienced this kind of consistently warm-to-hot weather before.  Another interesting tidbit:  every July-August period in the past decade has been above 70* F.  In contrast, our normals in the late 20th century were in the 68-69 degree range.  So it’s safe to say that the climate of NW Oregon and SW Washington has fundamentally shifted.

Here are July-August data for The Dalles Airport:

 

 

Here the results are even more stunning:  nearly TWO degrees above the old record.  The Dalles didn’t quite break its hottest month record from July 1985, but it came very close in both months this year.  While it’s fashionable to complain about how hot this summer was on the west side, I’m very grateful not to live on the east side anymore!

Something is up with our climate in the Western U.S.  Recently, we have been warming much faster than the planet as a whole.  This tweet by Brian Brettschneider sums up the extreme change:

Many locations have warmed between 3 and 5 degrees F since the early 1970s!  This is in contrast to the roughly 2 degrees of global warming that we have seen.  There’s been a similar dropoff in summer precip:

The two trends sure seem strongly geographically coordinated.  It seems to fit the narrative that the Four Corners ‘heat dome’ is much stronger than it used to be, and extends further northward in the summer months.

Perhaps this is a short-term hot cycle, laid on top of the long-term warming trend.  If that is the case, we should see some more reasonable summers return in the next few years.  If not….well, it would illustrate that climate change affects different regions differently.

SUMMER’S LAST STAND

Now it’s September and fall is quickly approaching.  But we have one final shot of hot weather coming up this weekend, beginning tomorrow Friday.  A strong Canadian high pressure is going to expand southward into Montana and the Northern Rockies tomorrow; this begins to happen on a regular basis as we move deeper into the fall.  That turns our surface winds to an easterly source by tomorrow morning.  Here is the WRF-GFS surface pressure map for 5am tomorrow morning:

By 5pm Friday the east wind gradient strengthens through the Columbia Gorge:

Then 5am Saturday:

At the same time, a thermally-caused trough builds up from Northern California and SW Oregon.  That sets the stage for an unusually hot, dry and windy day Saturday.  Slightly cooler air coming through the Gorge should hold Portland to the mid-90s, but Salem and Eugene could be in the 98-100 range!  That’s not unheard of in the 2nd week of September, but it is somewhat uncommon.

Of bigger concern will be the fire risk.  We haven’t had a soaking rain in the region in nearly three months.  Now a fairly strong east wind is developing over all that dry forest land.  This is the classic pattern for nearly all of our major west side fires & firestorms, including the Labor Day 2020 megafires.  The east wind probably won’t be quite as strong this time as it was two years ago.  Nonetheless, PGE is planning to shut off power in parts of the Cascade foothills & Western Gorge tomorrow and Saturday, as a safety measure against active power lines breaking and starting a conflagration.  A Red Flag Warning has also been issued for the Willamette Valley & Southwest Washington because of the dangerous fire pattern.

Needless to say, if you have outdoor plans this weekend, skip the campfires or anything else that could ignite the landscape.  Pack some cold food instead!  We don’t want to end up like Weed, California or the Galice area in Southwest Oregon.

The good news is that the wind dies down Saturday evening.  And beginning Monday, it appears that normal early fall weather will FINALLY arrive, with temps only in the 70s.  But it’s still unclear if we get a soaking rain soon.  If not, that could pose a problem if strong east wind develops again later in the month.

Be safe out there this weekend!  -Karl