Historic Heat Wave This Weekend; Could Be Hottest Ever in Portland

9 p.m. Wednesday…

This is it folks!…for days our weather models have been insisting we have a major heatwave on the way. In fact, for the past three days they’ve been forecasting never-before-seen numbers (hot) for parts of the region. Typically as we approach an extreme event (cold, snow, wind) models clue in a bit more and get more reasonable. But in this case they’ve looked almost the same for days. The extreme numbers aren’t going away. So we’ve gradually been upping our forecast high temperatures for the weekend as confidence grows. After some consultation with the rest of the weather team today, we’ve decided to go with an all-time record high in Portland this weekend. That would be HOTTER than 107 degrees. Here are the all-time records for some of the I-5 corridor cities and the year it happened. Notice they are all between 105-110. Downtown Portland records have the same 107 degree record as PDX.

First, for those of you not wanting to get into the meteorological details…


  • What could be the hottest heatwave on record in the Portland area (and much of northern OR/southern WA) arrives Friday and continues through Monday. At the very least, this will be one of the top 3 heatwaves in our area. Very warm temperatures, 85-95 degree temps, continue through the rest of next week.
  • Expect three 100+ days in Portland, and they may all be 105+
  • I’m very confident we’ll hit 106-107, and think 110 is quite possible for the first time here. Records go back to the late 1800s.
  • Humidity will be reasonable at first, but humidity will be up Sunday & Monday…it won’t be a totally dry heat like we tend to get late in the season (September).
  • Overnight lows may be the warmest on record in Portland too. Low-mid 70s Sunday and Monday mornings. That means homes/apartments will remain dangerously warm with no chance to cool off. Typically we see reasonable overnight temps in our area.
  • The only place to cool off will be the coastline…more like 75-85 out there over the weekend. Most likely you won’t be alone if you want to play on the beaches
  • I do not expect any sort of strong wind anywhere in the Northwest. Wind will be relatively light Saturday through Monday

The forecast could still change a bit, but all this is based on what we’re seeing just 2-3 days ahead of the event.


When I was 12, we suffered through the great August 1981 heatwave. I was living near Mt. Angel at the time. We spent a few days mainly down in the basement. Almost no one had air conditioning back then. Then when my career began in 1991, just out of college, I wondered when we might break that all-time 107 degree record in Portland. It was only a matter of time, but I didn’t think it would take another 30 years! I’m feeling pretty confident this evening that it’s finally going to happen.

A large and very strong upper-level ridge will begin developing just to our west tomorrow

Then by Saturday the heights really soar.

At this time, most models are forecasting 500mb heights over 597dm over southern British Columbia. Meteorologist Ryan Maue had a great tweet last night, mentioning that this would be an all-time record up over that area. And having a closed “dome of heat” just to our north keeps us in easterly flow from high in the atmosphere just about all the way down to the surface. You can see the WRF-GFS cross-section for Saturday afternoon through next Wednesday shows that easterly flow from Saturday through Monday afternoon.

850mb temperatures soar to +21 (C) Friday over Portland, +25 Saturday, and right around +30 both Sunday and Monday on operational ECWMF/GFS models. Ensemble averages from the ECWMF keep Sunday and Monday around +27 to +29. Anything above +28 is an all-time record for our area. The 850mb ensemble chart from the 12z Euro run shows the massive heat spike with the ridge. Very high confidence of +27 or above Sunday PM.

Down at the surface, a textbook perfect thermal trough develops Saturday. This is the WRF-GFS. Weak easterly flow through the Gorge, weak onshore flow right along the beaches. Almost no wind in the valleys. This, along with totally sunny skies, plus very dry air overhead, should lead to a very hot day.

Then Sunday…the thermal trough is right over the western valleys with a (10-20 mph) easterly wind through the Gorge.

At that point 850mb temps are somewhere between +27 and +30. THIS should be the all-time record hot day. Then on Monday things change a bit. A southerly surge of cool marine air is moving up the coastline and beginning to pour into the southern Willamette Valley. This COULD be a day where Eugene is 10 degrees cooler than Portland.

Onshore flow picks up that evening and we drop at least 10 degrees Tuesday. This is all pretty straightforward. But what has been shocking meteorologists is the surface temperature forecast from all the models. The ECMWF operational model looks like this. Crazy hot, exceeding Portland’s all time high by 7 degrees Monday afternoon! Most shocking to me is that the Euro generally has cooler surface temps than expected during warm spells. For example we’re going 97 on the day it’s forecasting 92. It’s hard to believe that would hold with those extreme temps Sunday/Monday, it’s not going to be HOTTER than 110 or 114.

Much better nowadays is to use ensemble forecasting…in this case 51 different members of this Euro model. This is just about what we are forecasting, accounting for the typically low Euro readings by adding a couple of degrees to most days over the next week.

Hopefully I’ve given you some reasoning for my “hottest forecast ever” here. Buckle up for a crazy hot weather ride!

I’ll be working right through the weekend and next week. So make sure you are following me on Facebook: @marknelsenweather and Twitter: @marknelsenKPTV. I will be updating those much more frequently than this blog. Most likely I’ll get a fresh posting done again Friday morning, if not tomorrow evening.

Chief Meteorologist Mark Nelsen

62 Responses to Historic Heat Wave This Weekend; Could Be Hottest Ever in Portland

  1. Robert Waltemate says:

    I’m not sure that here on the east side of the Long Beach Peninsula will cool off as much as it says it will. Is there going to be an Easterly flow out of the Columbia River? If so I bet we stay hot. What do you all think?

  2. Robert Waltemate says:

    House doesn’t have AC, but the 1998 motor home does. Too bad I didn’t get it up and running BEFORE it was 130 degrees inside it. I don’t ever remember it getting this hot here near Long Beach WA. My weather info on wunderground Kwalongb36. Too 🔥🥵!

  3. Patrick B. says:

    The thing that gets me is we will still be in the 90’s all week after this heatwave, actually it will still be a heatwave. Those overnight lows will probably be some all-time records too.

    • Joshua Lake Oswego says:

      A lot of records are going down. Some all-time, some June, some daily.

      It looks very possible that we will break the all-time temp record on consecutive days Sunday and Monday. Monday could get unfathomably hot if the marine push is even slightly delayed.

  4. runrain says:

    Still around 80° at 9pm. I wonder if tomorrow might make it into the upper 90’s. NWS says 94°. Mark says 96°.

  5. JohnD says:

    Pretty darn exciting, especially for those of us wondering if/when the PDX 107’ record would “ever” be broken! I well remember the last time—like a lot of us!
    Otherwise, the hottest I have personally experienced was 118’ @ the Furnace Creek NP Visitor Center in Death Valley a few years ago.
    (The official high there that day was 121’!)
    The experience was especially compelling because the day before we had summited Mt Whitney directly to the west in cool air heights. Also remarkable going from 14,500’ to <-200’ elevation within a hundred mile or so lineal distance. Incredible geography/climate there.

  6. Hank says:

    all current temperatures forecasted for salem Keizer on Sunday, from all models i can get, and all of the websites that I know of
    18z gfs 114
    Weather.com 115
    Accuweather.com 115
    18z Ecmwf 114
    18z gem which is on crack 104.7 expect much more than that
    Access-g 18z 112
    18z icon 113
    18z Norway 114
    18z gfs-mos 110
    Weather.gov 109 gov always goes low, we’re definitely getting record
    Weatherbug.com 112
    Timeanddate.com 111
    Weatherforyou.com 109
    Weatherstreet.com 111
    Theweathernetwork.com 109
    Weatherwx.com 113
    Myforecast.co 111
    Weather-forecast.com 113
    Worldweatheronline.com 113
    Weatheravenue.com 110
    Original record 108 and only one thing shoots under that. This is very interesting, I’ve always wanted to feel a record high on my skin, warmest I was ever outside during was 105.
    Stay cool out there folks, and I’ll do another one of these for the 00z tonight.

  7. Weatherdan says:

    Where are all the people hoping for an epic heat wave? In the Winter this blog is chock full of those wanting an epic snowstorm or windstorm or freezing rain event. Actually extreme heat bothers me less than the other 3. I lost power for 8 days in the epic ice storm back in February, so this heatwave doesn’t seem as bad to me. I do hope everybody stays cool and safe for the next few days. Also happy Independence day one and all. Peace.

    • Hank says:

      I want us to get the heat wave, honestly I like any weather event.
      I want to feel 116 degrees on my skin, warmest I was ever outdoors during was 105.

      • runrain says:

        I got a 115° in Phoenix once. I was there for a graveside funeral in August 2017. Fortunately it was in the morning. Went up toward Payson afterwards where it was in the balmy 90’s. They at least have trees there.

        So today overachieved most forecasts. Does this have any bearing on the upcoming heat? Most are still sticking with 105° or so on Monday too.

        • Hank says:

          Unfortunately I live in salem metro (north part of it) so the odds I will experience Monday heat is so low, so I’m just hoping for Sunday to be hot, on the 00z gfs a couple days ago my town on Monday was 120 and at that moment warmest spot in the world. Unfortunately that won’t happen. Well its a .5% chance.

      • Mike says:

        I was in Tucson when it set the all time record of 117, and Phoenix airport shut down because planes have a top temperature of 120 to take off and it was 122. Trust me, I spent 37 summers there, and every degree above 105 makes a difference. People are likely to die in this one, either jumping into very cold water or not understanding heat stroke. If this is not the hottest time of year, I would say the place is in trouble, and the summer season is way overrated. Next life, I’ll pick Duluth.

        • runrain says:

          You are so right on in your words. I’m really concerned about the toll this forecasted heatwave will have on people and pets too.

        • Hank says:

          Weatherdan, but people will also lose power to the heat wave since what i call it a (electricity overdose) which in my opinion having no power in 110 degrees is worse than during an icestorm
          Since atleast you have blankets in the cold…. in the heat…. well there’s no cold blankets, honestly -10 degrees without power is better than 110 without power

  8. Evan -- Cedar Mill says:

    I smell a bust for Monday.

    • Joshua Lake Oswego says:

      Probably south of Portland, but we might get up into the 100s again before the cooler air reaches us. It’s a race.

      I’m going with 105, 111, 106 for Saturday, Sunday, Monday. Monday has the highest variability of course. Then, a few 90s and back to 100s for the holiday weekend. There is no end in sight.

      This is devastating to our native plants and trees after a historically dry spring and a couple of years of drought conditions.

  9. Evan -- Cedar Mill says:

    Onshore flow is such a buzz kill whether it be cold or hot.

  10. JERAT416 says:

    My prediction is we get to 108, and not any higher at PDX. All this for one blasted degree above the record.

    • Evan -- Cedar Mill says:

      I know. If you’re going to break the record may as well go all out and hit 115F or 120F.

  11. 5OClockCharlie says:

    PGE saying it can handle the load… I sincerely hope so. I’d be lying if I said I wasn’t extremely nervous about that.

    I ordered a generator last week when I saw hints of this coming, but it won’t arrive until Monday (assuming it’s not “delayed”).

    The insulation in my house walls might as well be paper thin… the inside of my house typically goes 10 degrees lower at best than the outside temp – without A/C. Which means if the power goes out, not only am I going to suffer immensely but any temperature-sensitive foods/medicine will most likely need to be thrown out. I have no idea what it will do to my laminate wood floors.

    To summarize: I hope (pray really) this forecast is a major bust!

    • Hank says:

      Yeah on one of my comments last night on this post, I was pointing out what your saying. Since oregon is going green with energy, we have way less electricity, some spots have already had like a Texas situation, limited power or random temporary/long outages, and since air-conditioners take alot of electricity (for alot of people air-conditioners use more electricity than everything else they use combined) and then Saturday-tuesday everyone with fans air-conditioners ect will be on blast, but atleast there won’t be hot showers, but that won’t do much, since fans and air conditioners are nearly sold out, means there will be record a out of air-conditioner and fan usage, all on blast = no power.
      TLDR of this comment, mass usage of air-conditioners and fans + less power supply from going green = no power.

      • Mr T (Stayton Oregon) says:

        I know I sound like an annoying fly but “Hey listen!” to quote Navi: We had a brutal heatwave in 1981 that was the ‘record of all records’ and I don’t think the grid had any issues though region wide we set all time water usage.

      • 5OClockCharlie says:

        That’s a good point. I didn’t think of the green energy movement, but does that necessarily translate to less available energy? I haven’t been following how Oregon’s infrastructure has changed in that regard. Your point still stands though. We have nearly double the population we had in 1981 and if the energy infrastructure hasn’t been updated to meet that demand (and over-demand).

        I could see your scenario being a reality; although given PGE’s confidence I would guess it’s still in “unlikely” territory. On top of that, rubusleucodermis made a great counterpoint that electricity usage here peaks in the winter and most likely surpasses what we’re expecting for this heatwave. We’ll see..

        • Hank says:

          Yeah especially the past few months we’ve been going more green, and I’m just preparing for the worst, and pointing out a few facts for people to understand the possibility that could happen, I don’t think its likely to happen, but being prepared is safe. And also I have a question, I noticed less stock of water bottles at stores lately, and I know oregon is having a shortage of chlorine, is that what is leading to less water bottles?

        • Mr T (Stayton Oregon) says:

          I AM concerned about water usage though. The 1981 heatwave really tapped our resources.

      • W7ENK says:

        Without getting into specifics, there are two things majorly wrong with your statements:

        1) “we have way less electricity”

        That is absolutely incorrect.

        2) “some spots have already had like a Texas situation, limited power or random temporary/long outages”

        If you’re talking about in Oregon (or anywhere in the PNW), this is a flat out lie.

        • Jeff says:

          It happened in Keizer on Saturday

        • Mr T (Stayton Oregon) says:

          I think the big concern is water usage and hopefully nobody experiences any broken lines from either the heat or a contractor doing something they shouldn’t be do to heat stress.

        • W7ENK says:

          I can absolutely 100% guarantee you that any power anomalies in the Keizer area were not the product of an inability to generate or supply power by the electrical utility.

    • Electric utilities in the PNW are winter peaking, and a/c draws less power than resistance heating. Therefore the claims of PGE (and other utilities) are believable.

      • Hank says:

        Mr t, back then we had more electricity since we weren’t going green, and there was way less air conditioners back then, and this heat wave will be hotter. I rest my case

        • Hank says:

          And also there was less population back then, and I’m just trying to be prepared for the worst, that way if it happens the people prepared for it would be doing better

        • Let’s try physics and logic. Review what I just said, then ask yourself: Were there rolling blackouts in any recent cold spell?

        • Mr T (Stayton Oregon) says:

          I think cold spells are the more danger this winter if we don’t do something about the lack of electricity. We haven’t had any true cold spells in recent decades. 2008 didn’t get below 25F much and 2010 was a ‘moderate’ cold wave whatever the hell that means.

          A 1972 situation would be disaster in the making as California would severely tap into our grid as everyone cranks their heat up.

          California homes (even northern) generally only have a furnace in the hallway though mountain locations tend to have propane or gas.

  12. Jake says:

    The 00z GFS shows 114F for Monday….

    The fact it wants Monday to be the hottest day now gives me hope maybe there’s some disagreement among the runs. Where before it was Sunday. But, not holding my breath reason being:

    1) This isn’t Winter, and we’re not looking at a forecast for snowstorm chances where things fall apart easily.

    2) Urban cities by design hold in heat. This again makes heatwaves more predictable. We’re at a time of year where we have the longest days of the year. So there’s ample sunlight / angle.

    So unfortunately, I’m convinced this isn’t about breaking records; it will be more of by how much and how often.

    • Zach says:

      It shows 114F for Sunday. All the models are now backing way off for Monday’s temp (as in closer to 100)

  13. Roland Derksen says:

    It looks pretty likely that we’ll see at least an equal temperature with what happened if late July 2009 here. (i saw the high 90’s). But it depends on the wind- just a shift toward the SW, for example might keep temperatures down a bit.

    • Zach says:

      Yeah its a delicate situation. Could be a total bust when you are depended on a light wind this much.

  14. tim says:

    The icon model is definitively cooler then the gfs for next week and is usually more accurate than the gfs from what i gather, correct me if im wrong.

  15. Hank says:

    All weather models and websites for Sunday in salem/keizer
    Weather.com 115
    Weather.bug 112
    Accuweather 115
    Weather.gov 107
    Timeanddate.com 111
    12z gfs 113
    12z ecmwf 114
    12z gem 105, but strangley showing Monday 109
    12z Access-g 112
    12z icon 113
    12z Norway-ecmwf 112
    12z gfs-mos 115
    Weatherforyou.com 107
    Weatherstreet.com 111
    Localconditions.com 107 but I think this is weather.govs model
    Theweathernetwork.com 109
    Myforecast.co 112
    This is a warm forecast, i really hope the lack of energy and mass usage of air-conditioners doesn’t lead to power outages.
    Stay cool out there folks, but not too cool since we might lose power.

  16. Joshua Lake Oswego says:

    Today’s 12z GFS is the new single worst run of all-time. It never gets below the mid-90s until almost two weeks out. 4 straight days in the mid-100s again starting late next week.

    How is it even possible to consistently be 15-30 degrees above average?

    Tanis, you’re great with statistics. What are the odds of what is happening? How many standard deviations from normal is Sunday’s forecasted temp?

    • Tanis Leach says:

      This seems to be somewhere between a 1/50 and a 1/100 year summer heat wave at the current climate. Using the most recent forecasts for the local 5 (TV stations plus NWS) plus my own, that would lead to a forecast anomaly of +31 to +35. The only other times where Portland has had a +30 temperature anomaly was May 28th 1983 (100 PDX, 103 downtown, average back then 70) and April 27th 1926 (93 downtown, average back then 63). It was only a matter of time before a +30 anomaly would happen during the summer. Granted, since both of those were in the springtime, they couldn’t take full advantage of the maximum sunlight like we are now.

      As for standard deviations from normal: for the day: 4 standard deviations (about 99.9% of June 27th’s will be cooler).

      • Joshua Lake Oswego says:

        Thanks, Tanis. Great insight.

        Lucky us. A 1 in a 1,000 day coming bookmarked by two close to 1 in a 1,000 days.

      • Tanis Leach says:

        I should also note since I looked into it. Full average return period for the warmest day in summer. The 50 and 100 year return period is estimated and subject to change as I look further into it in the future:

        2 years: 101°F
        5 years: 103°F
        10 years: 105°F
        25 years: 108°F
        50 years: 111°F
        100 years: 116°F

        This is separate from any given day, which has a much lower odds of reaching any said temperature. What may be 1/100 warmest summer day is closer to 1/2500 for only if that given day was taken.

      • Mike says:

        4 sd significance depends upon the distribution. It does mean that at least a 1-(1/sd^2) or 15/16 (93.75%) percentile.

  17. tim says:

    some good news the 12z icon and gfs are backing off on the heat a bit
    for monday and beyond.

  18. Ken in Wood Village says:

    If the models are correct, this heatwave will be historic 😳 I’ve lived through both heatwaves and I didn’t like it then and I’m not going to like this one either. My job is only allowing us to work a half day Monday because we don’t have A/C in my work area. Let’s hope we don’t see the forecast highs…lol. Stay cool 😎

    • runrain says:

      Um, without A/C they should be giving you all day Monday off. Remember, the overnight lows will be very warm, allowing for almost no recovery.

      • Ken in Wood Village says:

        Yea, they have done that in the past. I just don’t have vacation time to take off so I’ll work for as long as I can in the heat.

  19. Evan -- Cedar Mill says:

    Unfortunately onshore flow will stop the heat dead in its tracks on Monday.

  20. Jake says:

    I really hope this backs off in the next 24 hours and we see 98 ~ 101 by a miracle. So much agreement among weather models though. That is not happening imo.

    I’m very concerned for my folks / siblings. Doing this to their a/c unit for the home, setting it to 85F and hoping above all it doesn’t go kaboom’.

    • Zach says:

      I think one day in the 105-110 range is pretty much a lock now. Most likely Sunday. Maybe 111-115 depending on thermometer placement. Granted there is always that small chance there is a bust.

      Fortunately though Monday is starting to look better than it did a couple days ago. (under 110F)

  21. Tanis Leach says:

    So I dusted off the video recording and editing software (its on my old computer), and the microphone. Thought what very may well be M.O.A.H (Mother of all Heatwaves, hat tip located in description of video) was enough to justify one. The result is this video. I admit I’m a bit rusty already. Any tips are appreciated. https://youtu.be/e7ryCTI2fIw

    Each section timestamped for those that just want a specific piece of information.

  22. Hank says:

    Wow! That’s a warm forecast, its showing 113 right now in salem keizer on sunday, and for a few days now the gfs and Ecmwf has shown us atleast 112, But its been hard to forecast monday in salem Keizer, since we might or might not get a good offshore flow on Monday, if we do get offshore flow, im forecasting from 115-119 or without offshore flow 97-103, either way we will very likely get atleast 109 on Sunday, which would break the record. And a big problem I’ve noticed, it already happened in a few spots, are brown outs, where its temporarily out of power or limited power, since the lack of energy in oregon and major air conditioner usage, on Saturday-Monday it will be even worse, and then its an infinite loop, if the power goes out, everyone tries to use it which makes it impossible to come back on.
    Stay cool out there folks.

  23. tim says:

    Interesting that seattle will not tie or break the all time record of 103 but most places will even in BC, not enough offshore flow must be the reason.

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