Marine Air Cools NW OR & SW WA; Drizzle Spots Thursday AM

June 30, 2021

9pm Wednesday…

That was quite a change today wasn’t it? For the first time in a couple weeks we totally busted the forecast. The marine layer was thicker than I expected…up around 4,000′ deep. That meant we never saw a total breakout into sunshine. Sure, a few sunbreaks here and there but that’s about it. After 14 days of 80+ weather, we finally saw a cooler day, only reaching 79 in Portland. That 14 consecutive day stretch was a new record for June in Portland; one of many records set this month.

June ends as the hottest on record, just edging out the very hot June 2015. Final monthly temperature is 70.7, August 2015 was 70.3. That month was consistently hot, but this year was more extreme for a shorter period. 9 days at/above 90 ties the all-time June record as well. The 30 year average for an ENTIRE summer is 14 in Portland

The marine layer thickens slightly tonight and by sunrise tomorrow the view from space should look like this afternoon’s view…all gray west of the Cascades.

There has been a lot of thunderstorm action over central/eastern Oregon this afternoon/evening. Very active and hopefully we don’t get a bunch of new/large fires going. The dry conditions, temperatures, and thunderstorms make it seem more like early August. It’s going to be a long summer.

Very sad news today from the heatwave; dozens of people have died. At least 45 in Multnomah county alone. I think it’s safe to assume more will be found alone in homes/apartments over the next few days. It really got me down for a few hours earlier in the day. My mother came over to our house for a couple nights Saturday-Monday, just in case the electricity went out at her assisted living facility. It didn’t and she was fine of course. But I keep thinking of people dying in their homes, especially the elderly…all alone with no friends or family to help. You might be surprised to find more people die from heat in the USA than any other weather event

In Oregon it’s a bit different, the #2 killer after taking the ocean into account. In general, weather doesn’t directly kill people very often here. If you take away the ocean-related deaths, less than 10 a year. That changed dramatically with this heat wave.

It’ll probably take some time to process all the temperature reports from the big heat wave. We know Hermiston officially reached 118 in Oregon Tuesday. The Dalles and Richland also hit 118 in Washington. The Dalles airport, where readings are taken, is in Washington.

But did some location hit 119, or 120, or 121? Most likely one of the cooperative observing stations in the two states did. We will see. Our local (Oregon) AMS chapter is hoping to plan a meeting just for this historic heat wave. Maybe in September.

We are in the summer dry spell now with no rain in sight, other than some marine drizzle Thursday morning. 12z ECWMWF 24hr QPF forecast shows 2 out of 51 members produced a tenth or two…in the next two weeks! That’s about the driest it gets

That’s it for now; I won’t be blogging as regularly over the next month or so…it’s summer vacation time.

Chief Meteorologist Mark Nelsen

The Great 2021 Heatwave: Monday Updates

June 28, 2021

I’ve changed the format for the heat wave…come back to this same link regularly throughout each day for quick updates as we go through the rest of this incredible weather event.  Newest information FIRST. Remember you can follow me on Twitter: @marknelsenKPTV and Facebook @marknelsenweather and I’ll be on TV tonight at 4, 5, 6, 8, 9, 10, 11.

11pm Final Update

This must be just about the largest temperature swing we’ve seen from a marine push. 46 degrees cooler at Salem at 11pm compared to the 117 degree high. By the way, Salem tied Palm Springs today, and was only exceeded by Death Valley here in the USA.

9pm Major marine push = much cooler

The past three hours have featured a very strong marine push. Just about the strongest I’ve ever seen and it’s wonderful! This means a shallow layer of ocean air surged inland. We expected that to happen and models forecast it very well. Most of us have seen a 25-30 degree drop. Kelso has dropped 41 degrees! That’s 110 down to 69 in about 4 hours. That’s some serious free air conditioning. I’ve had a few people ask me what’s up with the haze? I think it’s from some large fires burning just across the California/Oregon border that was picked up as air surged up from the south. By the way, Portland reached 116 around 6pm. These will now be the three hottest temperatures in Portland’s history. Downtown made it to 114.


Today’s forecast worked out perfectly…in a bad way. Marine air is arriving too late to keep us from setting more all-time records in the north Willamette Valley. Here are the official highs. Notice Salem was within two degrees of the all-time Oregon high (119 Pendleton-1898). The Dalles (technically in Dallesport, WA) has tied the all-time Washington high temperature record of 118

Portland’s 115 degree high beat the old (pre-Saturday) record of 107 by 8 degrees! Downtown hit 114, beating that old record by 7 degrees. Basically this heat wave blows away all other heat waves and resets the historical record

Cooler air continues to flood into the western valleys with wind gusts 30-35 mph west of Salem and up toward McMinnville. The cooling has reached a Bald Peak to Aurora line on the south, and down to Scappoose to Woodland coming in from the north. The next two hours we’ll see a 10-15 degree drop in the metro area as the east wind disappears and is replaced by the southwest or northwest wind. By 10pm I expect most of the metro area to be in the 70s…get those windows open later!

That’s it for now…I’ll be on FOX12PLUS (Channel 13 or 49) 8-10pm, then back on FOX12-KPTV 10-11:30pm. See you there!


Salem has broken their all-time temperature record AGAIN this afternoon. 116 degrees at 2pm!

This is just ahead of the approaching marine air. 112 at PDX ties the all-time high once again. We are running 3 degrees hotter than yesterday at 2pm. Headed for at least 114 the next few hours. Marine air is flooding inland on the west side of the valley; it should make the big move now to 5pm. Regional temps…The Dalles is at 115, just 4 degrees short of the Oregon all-time record. Except “The Dalles” is the airport…across the river in Washington.

Hang on folks…much cooler air begins arriving just 4-6 hours from now…

I’ll be on TV from 4-7pm as we track the extreme numbers and cooler air arrival

11am Monday

It’s the last day, but this heatwave is going out with one last blast of hot air. That will finish out this (hopefully) once-in-a-lifetime event. I would not be surprised to see one of the official Portland area weather stations hit 116 degrees.

Everything is proceeding according to plan. We’ve got 2-3 millibars (hot) easterly gradient still going through the Gorge to keep the extreme heat going through maximum heating around 5pm. Cooler marine air is poised in the Coast Range and pressure gradients are building between the coast and Willamette Valley. It’s 74 just west of Willamina, but 103 in Sheridan! Eugene is running noticeably cooler too. Hard to believe at 11am we’ve got temps well above 100 in a good chunk of the metro area.

And the regional temps.

850mb temperatures over Salem was a bit below the forecast this morning, at 28.0 degrees…we will see if the “coveted” +30 shows up in the afternoon balloon sounding.

Portland only dropped to 76 this morning and that is a new all-time record. But wait, there’s more. Many areas where it stayed breezy remained in the 80s! At my home it was 90 or higher all the way until 2am. I see a hilltop in Damascus only briefly touched 89 degrees before the sun rose.

Again, this is likely a once-in-a-lifetime occurrence. By the way, that record only stands if PDX stays at/above 75 degrees through midnight. It’s possibly the big surge of marine air heading inland this evening drops us below the mid 70s by that time.

Chief Meteorologist Mark Nelsen

The Great 2021 Heat Wave: Sunday Updates

June 27, 2021

I’ve changed the format for the weekend…come back to this same link regularly throughout each day for quick updates as we go through the rest of this incredible heat wave.  Newest information FIRST. Remember you can follow me on Twitter: @marknelsenKPTV and Facebook @marknelsenweather

9pm Final Sunday Update


Alright folks, we’ve got Portland’s warmest (hottest) night on record ahead, then slightly hotter tomorrow. Take a look at the all-time records set today. Pretty much every spot west of the Cascades in SW Washington and NW Oregon saw the hottest temp on record. Longview and Hood River numbers come in at a later time

Portland’s downtown observing location recorded a 110, which is also an all-time record. Those go back to 1874!

What’s ahead?

  1. Calm areas drop into the mid-upper 70s tonight. Windy spots only drop to 80-85 degree range…as if we’re in Arizona
  2. All model data tells us that tomorrow should be hotter than today, which is hard to believe. But it’s going to happen
  3. 850mb temps right now are around +28 to +29, and they go up to a record-breaking +31 to +32. This has never been seen in our area. Easterly flow INCREASES through mid afternoon Monday overhead, skies stay sunny. This all says several degrees of warming. I’ll stick with 114 for a high. That’ll be astounding if someone in the metro area gets within 2-3 degrees of Oregon’s all-time high (119 – Pendleton).
  4. Onshore flow sweeps up the coastline overnight = heatwave over. Then that cool air surges into the central/south Willamette Valley after noon. This should make for a cooler day south of the metro area. “Only” 95-105 south of Wilsonville-McMinnville line. Longview will also see a cooler day due to the onshore flow after about 1pm.
  5. The onshore flow will be some of the strongest we’ve seen in our area. A very shallow layer of chilly marine air surging inland trapped under a strong inversion (hot air overhead). Gusts 30-40 mph are possible 3-6pm from Sheridan to West Salem and north to Dayton. Yes, there could be a 40 degree drop from early afternoon to sunset for many of us! The cooler air arrives after 6pm in the Portland metro area, dropping us from 110+ to mid-70s by 11pm. It’s going to feel amazing…

Take a look at the WRF-GFS 5pm temperatures…112+ over a good chunk of the metro area Monday afternoon

Notice at 3pm we’ve got westerly wind beginning to pour into the central Willamette Valley. Salem is beginning to cool. Hot east/southeast wind from Longview down into the metro area

Then at 6pm things have turned VERY windy. Forecasting 8 millibars pressure difference between Lincoln City and Wilsonville! West wind gusting over 40 mph from Sheridan to Amity. Hot east wind still just barely going in the metro area. This is more of a “southwest push”; we’re not getting the real strong northwest wind coming up the Columbia River

Then at 9pm the southwesterly push has arrived in the metro area and hot east wind is gone. Gusts 20-30 mph will be ringing chimes in the southern half of the metro.

It will be a very shallow push, which means warm air overhead will mix down again Tuesday, just no extreme heat. We’ll like bounce back into the low-mid 90s Tuesday afternoon. Much better…

5pm Portland Makes It To At Least 112

High temperatures come in every six hours from the regular official reporting stations and here they are

Lots of 112s, but that’s also the current temperature at PDX. It’s possible we go a degree higher…we’ll see. Obviously that’s a new all-time record for Portland, well above the previous 108 record (yesterday) and long-standing 107 degree record. But look at the valley! Salem just blew past the 120+ year old record, by 5 degrees!

Astoria tied the 101 degree record, and Eugene set an all-time record too. I’ll have more with a detailed post about tomorrow and beyond by 8-9pm. The big message: 24 HOURS OF EXTREME HEAT STILL TO GO

3pm All-Time Record Heat, No Big Power Outages Yet

It’s 111 at PDX, the hottest temperature many of us have ever felt, including me. The same temperature as Phoenix at this hour…though at least relative humidity has fallen to 16%…it’s a dry heat. 3pm observations, notice all official stations are 108 to 111

All-time records have now fallen at PDX (again), Troutdale (again), Vancouver, Salem, and possibly Astoria where it hit at least 100. Eugene is only a couple degrees away. The Dalles at 114 is the highest I’ve seen at the airport sensor in my 30 years forecasting. The official record, I think those observations are downtown, is 115 degrees.

Huge temperature variations continue along the coastline. Just a couple miles inland it can be 105 degrees, yet around 70-75 right ON the beaches. Live view from our Shilo Inns Seaside camera shows a westerly breeze on the sand, that tells me it’s likely under 80 degrees in this spot. A lot of people. We’ve got two more hours of heating…typically. East wind has been blowing a few hours at PDX, and when that happens the temperature rise levels of a bit. That said, there’s no reason it couldn’t go up another 3-4 degrees. Hang on folks, we’ve still got 20-28 hours to go…depending on your location. I see just a thousand or so PGE customers out, that’s no worse than yesterday. Fingers crossed…


Hot…PDX is just passing over the 100 degree mark this hour. Troutdale, where east wind has surfaced, jumped to 105…at noon.

Check out Astoria…97 with a light northeast wind. Hoquiam at 100 is an all-time high temperature record.

Farther south along the Oregon coast, the extreme heat is either on the beaches or just a couple of miles inland. Example: Pacific City…67 on the beach but 97 over in the estuary area

Easterly pressure gradients continue to rise through the Gorge and across the Cascades. That easterly flow continues through Monday morning. As easterly wind surfaces in more spots, expect temperature spikes, but humidity drops. It doesn’t matter; either 102 and humid or 110 and very dry. It’s blazing hot everywhere except the beaches. Even Government Camp has gone over 90 degrees this hour.

I see PDX officially dropped to 73 degrees last night, the 2nd warmest night on record and the warmest ever in June.


The heat is on big time this morning, as expected we are starting warmer and heating up much more quickly. Current temps

And regional temps

What grabs my attention right now:

  1. 850mb temp (about 4,000′) over Salem was measured at +26.4 degrees (C) this morning. About 2 degrees below all-time record. Expected to rise to a record +30 by afternoon
  2. Overnight low was bad, but we did not set an all-time record in Portland. Down into the lower 70s
  3. Easterly gradient and breezes have developed as expected. Gusts 25-35 mph at Vista House, and wherever that wind surfaces temperatures are skyrocketing
  4. It’s 100 (at two separate wx stations) in Yacolt…at 10:18am. Astounding
  5. It’s 92 already on the Long Beach Peninsula (Ocean Park). Blazing hot for some of you on the coastline the next 6 hours. Mainly north of Pacific City.
  6. PDX is 88 at 10am, already 6 degrees hotter than 10am Saturday

Hang on…it’s going to be a rough day…

The Great 2021 Heat Wave: Saturday Updates

June 26, 2021

I’ve changed the format for today and Sunday…come back to this same link  regularly throughout each day for quick updates as we go through the rest of Saturday.  Newest information FIRST. Remember you can follow me on Twitter: @marknelsenKPTV and Facebook @marknelsenweather

9pm – Final Saturday Evening Update

What a historic day! Portland (and probably Troutdale) broke all-time temperature records…reaching 108 and 109. The final numbers…

And for the region

What’s ahead? In general the forecast hasn’t changed at all. Two more scorching hot days (hotter than today), then a strong marine push Monday evening brings in 70 degree air by 8-10pm west of the Cascades…it’s going to feel glorious. But, of course we have more record-breaking heat first. Tomorrow will be the hottest day south of Portland, due to that marine air arriving Monday midday down there. I expect at least 5 degrees warming from Salem to Eugene tomorrow, setting some all-time records. And at the coastline there will likely be a period from Noon-3pm on the north coast when temperatures soar. Tomorrow will feature conditions I never thought I’d see west of the Cascades. Temperatures to 110 and higher, a dry easterly wind, and nary a cloud in the sky. And keep in mind we’re starting much warmer tomorrow! It’ll take most of the night to get down below 80 in the urban/suburban areas

This will probably break Portland’s all-time warm low temperature. These are bit trickier to do because the weather data is collected for the calendar day (midnight to midnight). If we have a hot spell that ends with a strong marine push in the evening (that will happen Monday)? The late day temperature (close to midnight) could end up being cooler than the warm morning low. I’ve seen it happen in the past. But tomorrow night will be even warmer than tonight so I’m confident we will set this record.

For tomorrow, all models continue to agree that we’ll jump another 3-6 degrees, so I’ve put our forecast high at 112. The new 00z WRF-GFS shows a classic thermal trough from about Medford to Astoria in the afternoon

Easterly wind, although not strong, should be more widespread, and it’ll be windy in the western Gorge tomorrow. I’ve been watering my plants/lawn furiously the past two days in anticipation of that.

Look at those 104 degree highs just about touching the northern coastline beaches…plus 112 or so in the northern Willamette Valley

Then assuming cooling southwest wind doesn’t arrive until 4pm or so Monday, maybe a notch or two warmer. The east and southeasterly flow is very strong through midday Monday overhead and 850mb temps are 31-32 over PDX!

That’s it for now…I’ll be on TV at 10pm with lots more numbers.


Portland officially hit 108 today, hottest on record. More coming up by 9pm or so…dinnertime


It happened! PDX is reporting 107 degrees as the current temperature AND the high so far today. That ties the all-time 107 degree record from 1981 and 1965. I’d say about 1/2 of the time when the high is also the current temp at PDX on a sunny summer day…we end up a degree warmer. Unless the NWS puts out a special statement (seems likely), we’ll know for sure around 7:20pm. It’s quite possible today will go down as the hottest day in Portland’s history. Remember the downtown station has not gone above 107 either and those records go back into the late 1800s.

It’s possibly the 109 at Troutdale is an all-time record, looks like Vancouver is one degree short. A few thoughts

  1. Models nailed this, even better than we did. Even our “high” forecast of 106 has been exceeded. Models have been going more like 107-108 today. Sure enough, we’re doing a little better than Euro showed…which is disturbing for tomorrow.
  2. All models are forecasting between 3 and 6 degrees warming tomorrow as more of a widespread dry/hot easterly wind surfaces. That’s just unreal. Do the math and it’s obvious 110 is probably too low. Working on that now
  3. This has been an exceptional triumph of meteorological modeling. Models forecast all-time records being broken 5-7 days ahead of time.
  4. Power outages are beginning to pop up. About 3,500 PGE customers out


100 at PDX this hour, running 11 degrees above yesterday at 3pm. That puts us on track to hit our 106 degree forecast. Dewpoint is 67…very humid…yuck. Easterly (dry) wind beginning to surface in a few spots. Sure, it’s drier, but hotter. Troutdale and Scappoose jumped to 105 at 3pm! 102 at Rhododendron just below Government Camp is amazing for 1,600′ elevation. Heading toward max temps in the next 3 hours. Once drier air punches down into PDX, expect a temperature spike. Possibly the 107-108 models were forecasting was right. TODAY could be the day we set our all-time record. The drama…

Working on forecast right now and there’s a problem on the north coastline. WRF-GFS pushes easterly flow all the way to beaches and slightly beyond from about Tillamook north tomorrow. 100+ temps may be a possibility just inland from the surf from Long Beach down to Pacific City tomorrow. Maybe Astoria WILL break the all time record you see in the previous post. More later…


Looks like all is proceeding according to plan and no changes to forecast.  Rode my bike around 10-11 a.m.  Tolerable, but turning hot! 

Portland is 91 at noon; that’s plus 10 from yesterday at the same time.

Does that mean we’ll be 105?  Could be, but humidity is still high, dewpoint of 64…yuck.  That tells me the hot atmosphere overhead hasn’t surfaced or “mixed out” yet.  At some point within the next five hours, some drier air from above should surface.  When that happens the temperature will spike, then relative humidity falls.  Notice Yacolt is already 95???  It won’t matter by that time since we’ll be above 100 degrees.  Some other temps around the region are about what I would expect.  

Portland only dropped to 70 last night!  A record for the day, 2nd warmest ever in June.  The other two warmest were during the 2015 heatwave.  Of course that means you just endured the warmest night in 6 years.  Even out here at home in a rural area I only had a low of 63…rare.

Right now pressure gradients around the region are light northerly, or very light easterly across the Cascades.  Wind is light east in the Gorge, but stronger easterlies are arriving on many ridges.  I see Middle Mountain in the Hood River Valley is blowing along with Larch Mtn. and Three Corner Rock Washington.  That’s a sign the blistering hot easterly flow has begun overhead. I haven’t made the forecast yet, waiting to see what happens this afternoon with regard to raising tomorrow’s all-time high temp forecast. Morning GRAF & ECMWF models are the same…forecasting well above 110 both tomorrow and Monday as that dry east wind surfaces both days

That’s it for now.

Historic Blast of Heat Now A Near Certainty This Weekend

June 25, 2021

11pm Friday…

I’ve been a bit busy on TV this evening…7 shows!


The next three days bring an extraordinary and unprecedented surge of heat not seen during recorded history west of the Cascades. That’s a dramatic statement, but I’m quite confident it’s going to happen.


Our forecast hasn’t changed much, with a few caveats:

1) We should PROBABLY raise Sunday and Monday’s 110 degree forecast to 112-114. That’s because just about all models are pushing us into the 110-115 degree range both days. For tonight I left it the same. But does it really matter at this point? There’s always tomorrow to up things a couple degrees

2) Models just about all agree that the thermal low (hottest air) will still be over us 3-5pm Monday. That’s why we’ve upped Monday’s high temperature forecast to 110. It’s possible Salem, Albany, & Eugene are down closer to 100 that day

3) Excellent agreement that a major marine push drops us around 15 degrees Tuesday…which means that day will be similar to today, around 95.

4) Easterly wind might just touch the far northern Oregon and southern Washington coastline during the daytime Sunday. The result could be spots that spike well into the 90s. Anywhere between Tillamook and Long Beach. An example…it’s possible that at 3pm Sunday it’s 80 at the Tillamook Bay jetty, 85 at Garibaldi, 90 in Tillamook, and 100 at the eastern edge of the valley up against the Coast Range. Just an example.

4) This is a dangerous heat wave for those without air conditioning; we have never experienced these conditions in our area. You will not be able to cool down apartments/homes Saturday and Sunday nights. As mentioned in #1, it’s possible Sunday afternoon features temperatures 110-115 with a dry easterly wind. Add in low relative humidity in the metro area and you get absolutely unreal and hellish conditions for our area.

The 3 Day Forecast is crazy…

And the 7 Day…

For comparison, the hottest temperatures on record in our area

All records in the valleys are 107-109. We’re going to exceed at least some of these numbers

Eastern Oregon in general is hotter in summer so records are higher. Note Oregon’s all-time high is Pendleton at 119 degrees. We used to think Prineville shared that record (119), but it’s unlikely that ever happened. Washington’s all-time high is 118 at Ice Harbor Dam just east of the Tri-Cities.

Some of these records could be broken. Maybe Bend, The Dalles, or La Grande. We will see!

I’ll be working through the weekend and into next week. Stay tuned and make sure you are following me on Facebook: @marknelsenweather and Twitter: @marknelsenKPTV. I will be updating those much more frequently than this blog. 

Chief Meteorologist Mark Nelsen

Heat Wave: Confidence Growing We Will See Hottest Temps On Record In Portland

June 24, 2021

9pm Thursday…

This is just a brief post because NOTHING has changed meteorologically with the weekend forecast. All the points from yesterday are still valid. Just a tweak here/there


  • What will likely be the hottest heatwave on record in the Portland area (and much of northern OR/southern WA) arrives tomorrow and continues through Monday. And there’s a good chance we remain at/above 90 the rest of next work week.
  • Expect three 100+ days in Portland, and they may all be 105+
  • I’m very confident we’ll hit 106-108, and think 110 is quite possible for the first time here. Records go back to the late 1800s both at the airport and Downtown.
  • Humidity will be mostly reasonable…it sure won’t be “Bourbon Street Humid”, more like our typical heatwave humidity.
  • Overnight lows will likely end up 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 75-90 out there over the weekend. Most likely you won’t be alone if you want to play on the beaches. There’s a chance the far north coast makes it to 90 on Sunday…we’ll see.
  • I do not expect any sort of strong wind anywhere in the Northwest. BUT, some easterly wind will be felt over the metro area Sunday. Gusts 20-30 mph are possible. Enough to move an accidental fire along, but not enough to drop powerlines into trees.

I didn’t change any numbers for the weekend in today’s 7 Day Forecast, although we “overachieved” today with highs right around 90 in the metro area. I was thinking more like 86-87.

That boosts confidence in our extreme forecast numbers. Today’s forecast

850mb temperature forecasts remain the same (temp around 4,000′ overhead in Celsius). In fact, while making the forecast, I noticed both GFS & ECMWF ensemble averages matched through Sunday! +19 tomorrow, +25 Saturday, +29 Sunday (new record), +25-27 Monday PM. The only disagreement is over how quickly the upper-level low to our southwest Monday slides north offshore. Quicker movement Monday would lead to an earlier marine push = cooler high temps. Slower movement gives us another extreme day Monday. The most recent ECMWF ensemble average temps for Portland (near sea level) are just amazing. We were a few degrees warmer than forecast today. As I mentioned last night, we see that with Euro surface forecast temps in the warm season. That’s why we’re going 96 for tomorrow. Since the numbers turn so extreme Saturday-Monday, I’ve stuck with these numbers instead of going higher. I couldn’t imagine forecasting 111-114 for Portland…so I didn’t.

Check out the fresh 00z IBM Graf model, which handles warm season temperatures well. 108 Saturday, then around 114-115 Sunday! Just like the other models.

I’ve haven’t noticed this model “over-forecasting” heat in the last two warm seasons. Part of the reason we’re seeing such extreme temps (other than sun, offshore flow, and hot airmass overhead) appears to be the surfacing of that very dry subsiding air below the upper ridge. Notice the dewpoint drop both weekend afternoons. Sunday that would be relative humidity in the teens. The icing on the cake is the easterly wind Sunday. The GRAF is forecasting east wind to surface throughout the metro area that day (but not so much Saturday). It’ll be a “dry” 110 degree heat as they say…

In case you are wondering, the coastline WILL be cooler through this event. This applies to the northern Oregon and southern Washington coast…take off 5-8 degrees for Lincoln City and Newport

A few more numbers for you this evening. Portland’s all-time warm low temps. These are from the airport. With such a hot airmass, plus a larger metro area, plus a warming climate, it’s fair to assume we’ll be warmer than this.

This is dangerous for medically fragile or elderly folks…if you know any, please check in on them regularly!

That’s it for now, I’ll be on-air and online through NEXT Friday, the 2nd. I was already scheduled to work this weekend which is convenient. Make sure you are following me on Facebook: @marknelsenweather and Twitter: @marknelsenKPTV. I will be updating those much more frequently than this blog. 

Chief Meteorologist Mark Nelsen

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

June 23, 2021

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