It’s been a common saying in the Willamette Valley (including Portland) that you don’t need air conditioning in our climate. I’ve been hearing that since the 1970s when I was a kid. After the past two summers, many would disagree now.
Last summer we set a record for most nights above 60 degrees here in Portland…44!
Well here we are on August 28th, and now we’ve seen 40 such warm nights this summer so far. 
I think it’s quite likely we’ll see 5 more between now and the end of September so we’ll probably set a new record for a 2nd year.
So what’s causing this? One thing that isn’t…plenty of these nights have been under perfectly clear skies, so it’s not as if we’ve been seeing lots more cloud cover at night. That would sure raise overnight lows.
More likely it’s a combination of the both the urban heat island effect and our warming summers.
I can’t speak with any knowledge on the first because I haven’t check outlying areas (like Aurora, Battle Ground, Sandy etc…) to see if they have seen a similar rise in overnight temps. Common sense would tell you that overnight temps in summer in a rapidly growing metro area should warm; although PDX isn’t exactly surrounded by concrete and buildings. You can see the increase in warm nights since 1941
As for the warming summers…our summers have definitely been warmer, check out the June-August temps for the lower elevations of western Oregon. 
That’s Oregon climate zone #2. It’s also interesting that summers seemed to cool from around 1955 to 1980, then warm again following. With warmer summers, one would expect both warmer daytime highs and warmer nights.
Will this continue? History would say we will be in unprecedented territory if we had a THIRD summer of 35-45 warm nights. Looking at that chart you can see we’ve never had more than one or two summers like this before cooling a bit again. So it’s quite possible next summer is more reasonable. But the big picture also shows that in a slowly warming climate there will be more of this in the future…
My advice is to get at least a one-room air conditioner if you live in an urban area. They are more efficient than they have ever been and cheaper than they were 20 years ago!
Chief Meteorologist Mark Nelsen
FOX 12 Weather Blog 
Unfortunately, I am sleeping alone….
Nice run along the river this morning, although I could’ve used a few more clouds to keep the temperature down.
8/31/2014 Oregon (All) Temperature Summary
Warmest:
High:86 at ILLINOIS VALLEY(1389 ft)
Low: 63 at HEPP(311 ft)
Coldest:
High:45 at Timberline Lodge(7001 ft)
Low: 24 at KLAMATH NWR (4531 ft )
Largest Diurnal Change: 52 degrees
KLAMATH NWR (76/24 ) (4531 ft )
Heaviest Rainfall:
0.36″ at DW0380 Sandy(1600ft)
0.34″ at K7ZQU-7 Santiam(4790ft)
0.28″ at CW2654 Corbett(1050ft)
0.27″ at DW6879 Union(2792ft)
0.23″ at CW1038 Sumpter(4321ft)
78 today after a low of 56. Today was the 70th consecutive morning with a low at or above 50. This may end Wednesday when the NWS predicts a low of 48 in Salem. Our average high on September 1st is down to 80. Our sunset is before 8:00 PM. Still next Friday-Sunday may be in the low 90,s down here in the mid valley. NWS calling for warmer and drier through November. Fine with me. I’m hoping for a warm Winter to cut down on my heating bills. Peace.
I’m ready for another 08-09 winter!
I sleep great, at 1500′ it easily cools into the 50’s.
I’m with ya… However… You’re 1500’… If I remain at 350′ I’m not sure I’ll see another… I’ve seen two events in the lowlands… 40 years apart… But 2 inside 10 can always happen… Those times are included in “statistical norms” as well… 🙂
Boy has this blog sure died. Happy labor day all! Beautiful day here in Redmond today with sunny skies and a high of 70. More sun this week in fact all week and highs slowly climbing throughout.
Mt. Rainier Part II…headed back next week and again at the end of September 🙂
http://weathercrazy.smugmug.com/Landscapes/Rainier-Part-II
Great pictures Tyler. Beautiful area for picture taking.
Tyler,
Are you a summit climber?
My iPad blinked.
I am a novice but I have done Mt. Hood, Mt. Adams, etc. in the last couple of years.
Wish I could try Rainier.
Would be awesome!
August 31st. The first classic fall morning fog of the year up here.
It was bound to happen sometime soon. In fact, I expected it to happen a little sooner. Only going to get more of it as the nights continue to get longer and cool down more.
I suspect we may be in a particularly foggy fall up here in Puget Sound country, due to the warm summer doubtless causing water temperatures to be above normal. Warm water + cold early fall nights = lots of fog. Steam fog over the water and advection fog if breezes transport warmer moist marine air over cold land at night.
8/30/2014 Oregon (All) Temperature Summary
Warmest:
High:85 at PROVOLT SEED ORC(1180 ft) & MERLIN SEED ORCH(1144 ft) & Medford Viaduct(1360 ft) & EW1735 Central P(1285 ft) & ALKALI FLAT(2495 ft) & Medford, Rogue V(1329 ft)
Low: 65 at ECHO(683 ft) & BLALOK(277 ft) & BROOKS(187 ft)
Coldest:
High:49 at MT HOOD TEST SIT(5400 ft)
Low: 30 at KIRK (4519 ft ) & DIMLKE (4726 ft )
Largest Diurnal Change: 40 degrees
Beatty (75/35 ) (4320 ft )
Heaviest Rainfall:
1.20″ at BLAZED ALDER(3650ft)
1.00″ at MT HOOD TEST SIT(5400ft)
0.84″ at DW0380 Sandy(1600ft)
Certainly not scientific but the numbers below are a 6 day average (Aug 24-29) of reported Salem area lows.
Salem (NWS) 58.3
N Salem 58.3
Aumsville 56.7
Keizer 56.5
Turner 53.2
I cant help but think about all the variation in surface observations over time. Differences in equipment, placement, recording times, precision, vegetation, you name it. We all remember Eugene’s rain bucket controversy of 1996. http://zebu.uoregon.edu/raining.html
I would be interested in seeing 1000 mb sounding averages over time.
Moderate rain in Jefferson @0800.
8/29/2014 Oregon (All) Temperature Summary
Warmest:
High:94 at NELSON(2567 ft) & MERLIN SEED ORCH(1144 ft) & LAKE OWHEE AND O(2400 ft)
Low: 70 at JUNIPR(359 ft)
Coldest:
High:58 at HEBOWX Mt. Hebo(3160 ft)
Low: 30 at DIMLKE (4726 ft )
Largest Diurnal Change: 50 degrees
Horse Ridge (US (82/32 ) (4160 ft )
Brian Quigley, per your comment on previous post…Most of the “good” winters ie: 1948-49, 49-50, 68-69, 78-79, 79-80 were all considered “neutral” years. 2008 was a La Nina year. Here’s a list with classifications…
http://www.longpaddock.qld.gov.au/products/australiasvariableclimate/ensoyearclassification.html
76 and partly cloudy in Salem at 11:30 AM. Likely warming up to only 82 this afternoon. 57 under clear skies this morning. Looks dry but mild through next Wednesday before a warming trend.begins. Today through Wednesday looks to be about 76-82 with lows 56-62 and about.05 of precip. Then back to the 80,s and lows in the 50,s. Our Summer rolls on. Peace.
Ok, to add to the mystery. I see that Portland, Salem, and The Dalles are all warmer in the overnight hours. Yet, Hillsboro not in on the joke?
In June there were 20 days that were below 50 degrees, 10 that were 50-59 degrees for lows, 0 that were 60+.
In July there were 3 nights in the 40’s, 25 in the 50’s, and 3 in the 60’s for lows.
August: 3-40’s, 22 50’s, and 6-60+ degree nights for a grand total of 9 nights that were above 60 degrees for low temps.
I’ve heard about farming practices in the Salem area, maybe monsoonal flow being responsible for the humid/warmer nights around PDX/The Dalles. Last I checked, there wasn’t a real heat island effect in The Dalles, and Intel has pretty much paved over and built on the last remaining grass land around the Hillsboro airport, plus the huge explosion of housing out there. But for some reason, that defies logic, Hillsboro still cools off at night, while the daytime highs are comparable to PDX/SLE.
http://www.wunderground.com/history/airport/KHIO/2014/6/29/MonthlyHistory.html?
…On your second note, weren’t we in a negative PDO from the 1950’s through the ’70s? The positive through about 2010 when the PDO was showing signs of going negative again? Maybe we are about to enter a cooling phase that is taking a few years to take effect. Just an observation…I thought the PDO oscillated “approximately” every thirty year or so, unlike an El Nino La Nino cycle that occurs about ever 3 to 7 years.
I like the negative tilt from the high pressure in the east pacific from the models about 5-8 days out. Too bad that’s not happening in the dead of winter. Could have been an arctic blast lol.
We bought our first house in Aloha in March of 1992. That summer wasn’t too bad, so we decided just to put ceiling fans in the house. The next summer we had a heat wave one week and it was 85 degrees each night at 11pm, and I got 5 hours of sleep each night. After that we put in central air. We moved to our current house in November of 1996, and made sure we kept enough money in savings to add central air before summer. We’ll never be without it again.
This summer has seen more southwesterly flow aloft, bringing in warmer, moister air. Also, the last two years have seen the trade winds expand anomalously north. Coincidence?
8/28/2014 Oregon (All) Temperature Summary
Warmest:
High:97 at Medford Viaduct(1360 ft) & Hayes Hill (US 1(1640 ft) & ILLINOIS VALLEY(1389 ft)
Low: 72 at JUNIPR(359 ft) & John Day River B(305 ft)
Coldest:
High:46 at MT. HOWARD(7910 ft)
Low: 34 at DIMLKE (4726 ft )
Largest Diurnal Change: 48 degrees
ILLINOIS VALLEY (97/49 ) (1389 ft )
KLAMATH NWR (85/37) (4531 ft)
I’m amazed that Mark could talk about all the warm nights without mentioning the HUMIDITY.
Did you realize that The Dalles Municipal Airport (DLS) just reported the 2nd warmest July on record, and is on track for the 3rd warmest August? It’s also the warmest July-August period since 1967. THAT came as a bit of a surprise, since we didn’t even make 105 this July (compared with the 110 days we saw on several occasions in the 1990s).
With a near-record number of muggy nights this year, it’s small wonder that I’ve found it so uncomfortable. Let’s hope that Summer 2015 is a bit more reasonable.
Man, there’s not many simple pleasures in life that I enjoy more than sitting outside with a good cup of coffee at 6:15 am, in 60+ degree temperatures. Pretty soon it’s going to get too dark for those early morning shenanigans.
Urban Heat Island anyone? Just 6 nights at/above 60 here in Battle Ground.
Pics from just two days up at Mt. Rainier…the pictures don’t do it justice though!
http://weathercrazy.smugmug.com/Landscapes/Mt-Rainier-818-81914
Great pics as usual Tyler.
Awesome set! Makes me want to hike again soon
…. And maybe get a better camera as well 😉
No trouble at all. An open window and a small fan works wonders for me!
Some nights when we were completely smoked in and couldn’t do that, it was horrible in K-Falls without AC! lol
Luckily the brunt of the smoke has been done and over with.
Also, I didn’t even bother pulling my AC out of storage last summer. This summer, on the other hand…
Mark, you should run a chart showing overall relative humidity/dewpoints and compare that against the overnight lows. I think you’ll find a correlation. It seems as though our summertime atmosphere has been becoming more humid over the last couple of years…
Yeah the PNW had some very decent monsoon flow with impressive moist air.
I also observed here that I didn’t get all too many dry t’storms, I’d say normally more than half of my convection is non-wet throughout the year, but different story this year! A good chunk of them in July produced downpours, and all of them in August did the same.
It’s seems like it has up here too Erik in Southeast Tacoma at least. I watch the readings daily here on my weather console when I can.
Agree. Biggest complaint I’ve heard this summer has been the humidity, especially in the overnight hours.
I don’t have easy access to temps and dewpoints. AND, I don’t think this summer (at least August) was nearly as humid as last year.
Cold beer on a warm night is one of life’s simpler pleasures.
Right, gidrons!
hahahaha