The Big Heat Wave Begins

9:30am Thursday…

Hunker down (or find a cool river/lake to enjoy), it’s going to get really hot!  The NWS has a plethora of excessive heat warnings, advisories, and red flag warnings for most areas WEST of the Cascades from this afternoon through Saturday.


  • High temperatures the next 3 afternoons will be somewhere between 98-104 degrees in the lowlands of western Oregon and SW Washington.
  • We have never seen 3 consecutive 100 degree days (or even two) after the 15th of August, so if we get two or three that will be unprecedented.  That said, we’ve been quite close a few times in the past.
  • Breezy north wind today turns to a gusty easterly wind coming down off the Cascades and through the Gorge Friday.  That wind continues through Saturday morning, then it goes just about calm (hot!) Saturday afternoon.
  • Much more reasonable Sunday with highs at best around 90 degrees as a strong marine push begins
  • At the Oregon Coast, today will be much warmer with a few 80s possibly showing up, but FRIDAY is the scorcher with east wind pushing high temps well into the 90s for many towns.


Everything is on track this morning for a very late season heat wave.  Once we get past mid-August it’s very rare to hit 100 degrees.

A hot atmosphere has developed overhead.  850mb temps during the balloon sounding over Salem showed a +21.8 degrees, just what models have been forecasting.  They also say it’ll peak out around +24  to +25 for the next 3 afternoons with the trusty ECMWF forecasting those numbers.  That’s crazy hot, especially for 3 consecutive days with offshore flow.  I think the all-time highest August temp at 850mb is +27 during the 1977 heat wave.  It hit 105 in Portland that day.  So I’m pretty confident that we’ll get at least one day above 100 and we might possibly do all 3.  This is what we’re forecasting right now for highs at PDX and the records we should break:


Friday or Saturday will likely be hottest since 1) Friday has the best offshore flow and we start “pre-warmed” from today, but not so crazy windy that it holds the temp down a few degrees AT Portland airport and, 2) Saturday we start with offshore flow and then the wind goes calm in the afternoon, yet we don’t start to get a cooling northwest wind up the Columbia River.  Those are just about perfect heating conditions for PDX.

Offshore flow has already begun this morning, even at the surface there is a very light easterly gradient through the Gorge.  In the Cascades an easterly wind has begun with gusts to 30 mph at Three Corner Rock north of Bonneville and 30-40 mph gusts at the top of Upper Bowl Chair at Skibowl.

I expect temps to slowly rise through noon, then really take off.  During a heat wave in 2008 the temperature rose from 82 to 102 from noon to 5pm, proving that the warm air above can surface quickly!

As mentioned earlier, hitting 100 this late in the season is tough to do…in fact the last time we got above 100 in the 2nd half of August (or early September) was way back on September 2nd, 1988!  I remember shoveling corn and carrot slop on that day working at National Frozen Foods in Chehalis (my job for 6 summers in high school and college) inside the plant.  Geez it was hot!  Obviously no air conditioning in a place like that.  There’s nothing like warm carrot “goo” at 100 degrees.  Yet, it did allow me to get out of college almost debt free!


Stay cool…

Chief Meteorologist Mark Nelsen


28 Responses to The Big Heat Wave Begins

  1. NWS forecast high is now a more believable 91 for me. Something must have been acting up with their point-forecast software last night. Now 67 after an overnight low of only 65.

  2. Anonymous says:

    81 for a high here with a fairly strong northerly sea breeze. NWS now says 97 for me tomorrow. WTF? is going with 88 which seems more realistic. Either would be my warmest of the year. Looks like strong marine push is coming for Sunday and Monday, then more warmth.

  3. JohnD says:

    Thanks Mark. Just getting around to your recent post. Comprehensive and erudite as always! I was out hiking in the Gorge today. The car thermometer read 101′ at one point while driving home.
    B-t-w I worked at a similar Stokely Van Camp plant for 10 seasonal years during my own college career! I am much older than you–but still, kindred spirits. (My one time meteorological aspirations, alas went the way of liberal arts.)

    • JohnD says:

      Uhhhh, to clarify: 4 of those seasons were during high school! The other 6 through my BS and MA. Definitely grateful for the “bread and butter” that the cannery work provided! AND the experience–character builder–right!?

  4. Josh "The Snowman" from Gladstone, OR says:

    Of course this turns people on the road into complete Aholes too. Was over in Beaverton and had an Arab guy tailgating me real bad and then flipped me off when I turned. You would think this is tame compared to what he is used to. Take the mask off of your wife dude and relax.

  5. oldwxwatcher says:

    Guess the drier air got lost on its way to my location in East Portland today . At 3:45 PM it was 99.2° with a 62° dewpoint. That produced a heat index of 101°. Hope the east winds will make an appearance here soon.

  6. Garron 1/3 of a mile from Hillsboro Airport says:

    Lots of 100 degree readings before the 4PM reading with another 90 minutes of warming possible before we begin to “cool off” Mc Minnville, Hillsboro, Salem, and Portland all should be 100-104 today!

  7. Scooter says:

    101 degrees now here east of Oregon City. Tomorrow will be very interesting with todays heat build-up and more east wind and compression heating of off the Cascades. In the past I have seen it warm to 90 degrees by 9 AM, so hold onto your hats boys and girls!

  8. Garron 1/3 of a mile from Hillsboro Airport says:

    Wow, explosive heating going on! Hillsboro has cut it’s humidity in 1/2 going from 40% to low 20’s from 12:15 PM to 1:30 PM, while temps jumped from 84 to 97 in the same amount of time! 99 D/F at KHIO as of 2:30. Same time the Portland airport has dropped to 30% so far and 93 degrees. Seems like the west side metro dries out quicker at the start of this event. Salem sitting at 93 degrees, 30% humidity, while 99 degrees, and 22% humidity around the same time at the McMinnville airport, 2:30 PM. This is fun to watch how quickly it dries and warms.

  9. Garron 1/3 of a mile from Hillsboro Airport says:

    Hillsboro and Portland the is just starting to dry out. Dew points dropping below 40%, how low can we go??? 10%, lower maybe.

  10. 82F here the last I checked (11:50 am). I won’t see 100- that’s expected, as I never do. But 90F is possible. However, will we go higher than that? If so, by how much? My all time maximum temperature for August is 94F (August 8, 1978).

    • A bit of a SW sea breeze helping things out here. I’m at 86F which is slightly below what I expected at this time. Even cooler right at the Airport (YVR) which is right at the water’s edge: just 72F!

    • I maxed out at 81 today due to fairly strong sea breezes interfering with warming. NWS is going for 97 here tomorrow; I have a hard time believing that. says 88 which sounds much more realistic.

  11. runrain says:

    Astoria currently same temp as Portland with NNE winds picking up. Here she comes! The next three days will be miserable, yes, but for the true weather geek – fascinating! Let’s go for that triple digit trifecta and capture that Unprecedented trophy!

  12. Josh "The Snowman" from Gladstone, OR says:

    And lo and behold I have an attic job today installing air conditioning out in Damascus. Fortunately I started early and am mostly done in the attic. My temp-meter reads 103 right now up here. Stay cool all.

  13. pappoose in scappoose says:

    pappoose in scappoose says:
    August 18, 2016 at 9:28 am
    Area Forecast Discussion
    National Weather Service Portland OR
    841 AM PDT Thu Aug 18 2016

    SHORT TERM…(Today through Saturday)…Big change starts today and continues for a 3 day stretch as an upper ridge builds over the
    region, making it hot, hot, hot! Some may say sunny and miserable.

    Joshua Downtown PDX says:
    August 18, 2016 at 9:35 am
    Ha. I like the personal touch. I am in the sunny and miserable camp. Although, with it being so dry, it won’t be too brutal.

    pappoose in scappoose says:
    August 18, 2016 at 9:51 am
    I’m camping there too!

  14. Larry says:

    Stay hydrated, friends.

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