Hopefully you were able to make the most out of this chaotic and hot summer!  While I didn’t get to go storm chasing or camping or any “top tier” activities, I did get in several one- to two-day trips, including three visits to the Oregon Coast, a memorable road trip to Crater Lake, and an overnight stay in Seattle.  I also endured one of the two hottest summers in Portland’s history, roughly on par with the historic summer of 2015.  

There were two main factors behind my decision to move to Portland from The Dalles three years ago:  better cultural & social opportunities (weather friends, music, etc.), and the milder climate of the west side.  Unfortunately about half of that time has been hampered by the COVID pandemic, which has severely curtailed social life.  The other problem is that the heat I was trying to escape in The Dalles, has seemingly followed me as I moved west.  Two summers ago it was mainly warm, humid nights.  Last summer it was the mega wildfires.  And this year?  Brutal heat.

I remember experiencing 111-112 degree heat in The Dalles when I was in high school, working at the movie theater across the street from my home.  Never would I have imagined that someday I would endure even hotter temps while living in Portland – and do it with no air conditioning.  The 116-degree day in late June was truly dystopian; it’s a miracle I was able to fall asleep at all during those torrid nights in my 95-degree bedroom!

A SUMMER SUMMARY

As of Wednesday, September 1 – meteorological summer ended and fall began.  So now we have the official data for the months of June, July & August.

This summer’s exceptional heat was driven by one month in particular:  June.  This is a bit ironic, considering that Pacific Northwest summers normally center around July and August.  In fact, west of the Cascades, June has traditionally been somewhat cooler and cloudier than September!  This year though, the heat arrived early and arguably ended early:  we haven’t had a single day at or above 90 since mid-August.  So our summer peaked at least 2 weeks earlier than it usually does.  At the same time, it seems that recent winters have been coming later, with much of the cold/snowy action in February or even early March.

Below is a ‘chart’ of the monthly stats for various Pacific Northwest stations on both sides of the Cascades.  I didn’t include the coast because its summer temps are more influenced by ocean temperature (i.e. warm and cold ‘blobs’) than by any kind of upper-level atmospheric pattern.  The averaged daily high and low temps are given on the left, and the departures from the “new” 30-year normals are on the far right:  ‘+’ for warm, and ‘-‘ for cool.  Season averages and departures were calculated simply by averaging the three mean numbers and three monthly departures, and rounding accordingly; there may be minor discrepancies from the official data here!  

Summer 2021 Stats for PNW Cities

PORTLAND (PDX)

 

June – 82.6/58.8  Mean     70.7 (+6.5)

July – 85.5/60.6   Mean     73.0 (+2.8)

Aug – 84.0/61.0   Mean     72.5 (+1.9)

Season                Mean     72.1 (+3.7)

Days 90+                            24 (9, 6, 9)

 

EUGENE (EUG)

June – 82.4/52.0  Mean     67.2 (+6.3)

July – 88.9/53.9  Mean     71.4 (+3.6)

Aug – 86.5/55.2  Mean     70.8 (+2.9)

Season                Mean      69.8 (+4.3)

Days 90+                             39 (9, 18, 12)

 

MEDFORD (MFR)

June – 89.0/59.0  Mean     74.0 (+7.1)

July – 96.7/63.8  Mean     80.3 (+5.2)

Aug – 92.0/60.3  Mean     76.2 (+1.7)

Season                Mean    76.8 (+4.7)

Days 100+                         23 (8, 8, 7)

 

THE DALLES (DLS)

June – 90.0/61.9  Mean     76.0 (+8.9)

July – 93.7/65.7  Mean     79.7 (+5.0)

Aug – 90.0/63.9  Mean     77.0 (+2.9)

Season                Mean    77.6 (+5.6)

Days 100+                         22 (7, 6, 9)

 

WALLA WALLA 

June – 88.2/60.5  Mean     74.4 (+7.4)

July – 93.9/66.3  Mean     80.1 (+3.8)

Aug – 86.7/62.1  Mean     74.4 (-0.8)

Season                Mean     76.3 (+3.5)

Days 100+                          12 (5, 3, 4)

 

SEA-TAC (SEA)

June – 76.6/55.5 Mean     66.1 (+4.1)

July – 79.1/56.9  Mean     68.0 (+0.9)

Aug – 77.8/57.1  Mean     67.5 (+0.1)

Season                Mean    67.2 (+1.7)

Days 90+                           8 (3, 2, 3)

 

Now let’s take a moment to digest these numbers.  First of all, it should be clear that our historically hot June is what really “made” this summer exceptional.  At the same time, our hot June this year was not much hotter than a normal July or August!  Of course the heat wave at the end of June was unlike anything we’ve ever seen in any month, July and August included.  But from a monthly numbers standpoint, we basically just had “two Julys” this year, the second one (actual July) being a bit hotter.  Then August was just slightly hotter than normal.  

Secondly, July was more exceptional to the south and east of Portland, than in Portland itself.  There were a number of days when PDX topped out in the mid/upper 80s, but Salem and Eugene were in the low 90s.  We had just enough onshore flow in July, to keep NW Oregon and Western Washington from getting extremely hot most of the time.  (This onshore flow also explains why wildfires never got too bad in our immediate vicinity; more on that topic below.)  In fact in the Puget Sound, both July and August ended up very close to normal.

The third feature is Walla Walla.  Look at how its departures for July and August are less warm, relatively speaking, than The Dalles – in fact, August was significantly cooler in Walla Walla.  Earlier this summer I considered writing a blog about whether wildfire smoke would impact the West’s future late-summer climatology, by causing August and September to warm less dramatically than May, June or July.  In the end I kind of gave up on the project, given how much research it would have entailed.  But now those Walla Walla numbers make me wonder:  did dense smoke put a lid on their summer heat?

I don’t have smoke maps from July and August handy, but I clearly remember that the densest smoke during most of our big wildfires, was well to the south and east of Portland.  Eastern Oregon, eastern Washington and Idaho (not to mention California) have all had more smoke in the air than Portland or Seattle.  In particular, Walla Walla was probably deeper into the smoke “zone” than The Dalles was – being another 150 miles to the east.  (Maybe I will do an air quality/temperature analysis of the two cities in a blog this fall, if the weather is boring enough.)

One other thing not shown in the monthly averages, is that hot weather abruptly ended after the 15th of August.  In fact, if we don’t hit 90 degrees again at PDX in the next week or two, 8/15 will probably be our final 90+ day of the year!  While this definitely isn’t unheard of, it’s still pretty early for a final-90 date.  And a bit of a paradox, given how hot the overall summer was.

Here are the “divisional rankings” for June and July, which show the historic heat across the West.  Unfortunately the maps for August and the full summer aren’t out yet, but I will post an update on the blog or on Facebook when they become available.

(image credit:  ncdc.noaa.gov)

 

LOOKING AHEAD….

Summer-like weather didn’t end on September 1, obviously.  The first week of the month has been sunny and quite warm, even if nights are cooler than they were in July.  Indeed, one of the challenges with Portland summer climate analysis is that in some years, the really warm weather drags on well into September, and gets computed as part of the fall season instead.  The main difference, of course, are the somewhat cooler nights now than in midsummer: mostly low/mid 50s as opposed to upper 50s & low 60s.  

(spaghetti image:  Weathertogether.net/models)

We have two more warm late summer days on tap.  The atmosphere actually is supposed to warm up tomorrow afternoon, and reach about +20c at 850mb on Tuesday.  In the middle of July, temps of 20-21 degrees Celsius at 5000′ elevation could get us close to 95 degrees Fahrenheit at PDX.  Due to the weather September sun it will be somewhat cooler, but I still think Tuesday has a good shot of giving us one more 90-degree day for the year.  Today’s WRF-GFS model shows what appears to be hot easterly flow at 2,500′ over Portland and NW Oregon on Tuesday afternoon; which is good for getting hot in general.

(image credit:  UW Atmospheric Science)

There’s a very slight chance of instability and scattered T-storms Tuesday night as the pattern begins to change.  After that, models agree that we shift to cooler weather for the 2nd half of the week.  Temps in the 70s with more clouds than we’ve seen this past week.  At this point any rain showers appear to be light and spotty, though.  MAYBE there’s a chance of wetter conditions toward the 3rd week of September, but that’s still pretty far off.

 

FALL FIRE DANGER?

Northwestern Oregon and Western Washington have been extremely lucky this year when it comes to onshore flow helping to ease the fire danger.  Even during the great June heatwave, offshore flow was rather weak and dewpoints never got dangerously low.  (In fact, they got up to 70 in some places during the event where and when easterly flow was absent!)  That hasn’t been the case in the rest of the West; massive wildfires have been the rule in southern Oregon and California.

Locally speaking, could the worst fire weather still be ahead of us?  There’s definitely a chance that it could.  If we don’t get substantial rainfall in the next two or three weeks (let’s say at least 1.0-1.5″ in Portland), then a warm/dry east wind in late September or even early October, could spell big trouble for us.  And even if we do get those kind of rain totals, our drought is currently so deep that we might not be completely in the clear.  It all boils down to whether an east wind returns before serious fall rains arrive.  

Whether fall is cool and wet or warm and dry…stay safe everyone!  

Karl