Cooler Weather Wraps Up a Hot & Dry Summer

August 29, 2021

9pm Sunday…

Hopefully you enjoyed this last weekend of August? It was quite a bit different than the cloudy/sprinkles stuff we saw last weekend. Portland hit 87 both days

A very interesting month…blazing hot first half, then near to below normal the 2nd half

At this moment, it’s still the hottest summer (June-August) in recorded history at PDX. BUT, it’s only slightly above Summer 2015. Add in two cool days (tomorrow and Tuesday), and I have a feeling it’ll be a tie for hottest summer in Portland. Salem’s records go back into the late 1800s and it’ll definitely end up as #1 hottest there.

The drought continues of course. The six months March-August are the driest on record at PDX, totally blowing away the previous years. Hard to believe we’ve seen less than 4″ of rain since the end of February!

I did check and find that is NOT the driest six months on record at PDX. There have been just a few other years in which May-October rainfall was less than 4″ as well. But we’ve never had a spring/summer dry combo like this.


We are in a typical late summer or early fall weather pattern now. That means we don’t stay in long warm/hot periods but not much rain either. Forget the air conditioning…nights have been in the 40s/50s much of the past week and that continues. Weak ridging overhead gave us the warm weekend, now a cool trough drifts through southern B.C. the next 2-3 days. You can see the dip in the flow Tuesday up around 18,000′

That’s on top of a major marine push in progress. Already at 8:30pm much of the metro area has dropped into the upper 60s. The westerly flow is also pushing all fire smoke east; notice the plumes coming off Cascade fires this evening are all headed into the eastern half of the state. This is the most active I’ve seen those fires in quite a few days. More on fires in a minute

More onshore flow means highs only in the 70-75 degree range the next two days, but I don’t expect solid gray skies. Sun & clouds will mix.

Wednesday through Friday the trough moves east and atmosphere warms…we should be back in the 80s Thursday/Friday. It’s not a hot ridge of high pressure; no “heat dome”. Just an absence of any cool systems nearby. The Friday afternoon view


Models generally have some sort of upper-level trough swinging by around Sunday/Monday, but they are in great disagreement. Just taking a look at the ECMWF ensembles today, 21 of 51 members (a little under half) bring some real showers through Portland either Sunday or Monday. Of course that means more than half keep us dry through the holiday weekend. This chart shows each of those 51 members as one horizontal line on the upper half of the image. It’s 24 hour precipitation.

Anything with some color (not gray) means at least .10″. So details for next weekend are still to be resolved, but we know at least Saturday will be dry.


The cooldown and lack of thunderstorms the 2nd half of August has had a HUGE impact on fire weather. There has only been ONE big new fire in the state of Oregon in the past three weeks. That was the Fox Complex near Lakeview. No other new fire over 1,000 acres has ignited. Very good news. We still have 5 large fires (over 100 acres) burning in Oregon this evening, that’s down from around 10 a couple weeks ago. It’s 4 different complexes that started from lightning the first few days of August, plus the Jack Fire which began right around the 4th of July. That fire hasn’t seen much growth at all the last couple of weeks. But the other 4 keep burning steadily

The Bull Complex is an interesting one because it’s burning in a relatively small area between three of those mega-fires last September, maybe 5-8 miles north of Detroit.

That’s it for now…although I do have some “mixed emotions” news to share. Anne Campolongo has been a big part of our weather team for the past three years; the best weather team I’ve worked with. She’s one of the most professional people I know; smart meteorologist, friendly, great sense of humor, willing to learn, and really enjoys life. She came to us from Medford, just two years into a TV career after a meteorology degree. But now she moves on with 5 years experience in this business. Heading to the “big time” weather-wise! KCCI-TV in Des Moines, Iowa. That will be quite the severe-weather experience. Tornadoes, blizzards, damaging thunderstorms, etc… It’s also much closer to where she grew up in Ohio. So we’re sad she’s leaving, but happy she is headed to a good place. Goodbye Anne!

Is Summer Over? Not Really, But It Feels Like It!

August 22, 2021

9:30pm Sunday

What a tremendous change the past week! Take a look at high temperatures in Portland. 100s to 90s to 80s to 70s. Today we just barely made it to 70, which means we spent the whole day in the 60s. This weekend was the coolest we’ve seen in over two months.

I had a few days off last week, but working this weekend. I’ve had plenty of time to get up to speed and here’s what I’m seeing:

  1. We had our usual two month period of guaranteed warm/dry/sunny weather, but it was a bit early… June 15th to August 15th.
  2. The heat of summer is gone, and there’s no sign it’s coming back. Endless days of sunshine are done for this year. Sure, we should have plenty of warm/dry weather ahead, but expect marine air to flood inland at times too. Just like this weekend, we will have cloudy or mostly cloudy & cool days mixed in.
  3. We can still get up to 90 for about another month, but no model is projecting that for Portland through the rest of the month. We’re just 10 days away from September.
  4. I don’t see a soaking rain, or even widespread showers, for the next week

With 9 days left in “meteorological summer”, we’re still on track for the hottest summer on record. That’s both in Portland and Salem, but it’s going to be close with this recent cooldown. It may end up the 2nd hottest. Regardless, both cities DID experience the warmest 2-month period on record from mid-June to mid-August.

One surprise, and a mild forecast bust, was the heavier than expected showers today. Many areas picked up measurable rain, and .05-.10″ was not uncommon. Almost all of it was central/east metro

That makes August 22nd the 2nd day with measurable rain this month at PDX.


For at least half the time, we’ll be under weak upper-level “troughing” or a dip in the jet stream through the end of the month. Right now a chilly system is passing by to the north in British Columbia; excellent news with all the fires up there. Here’s the Canadian model’s representation of the current setup. Cool showers up north plus lots of cool northwesterly flow coming down the B.C. coastline into Oregon/Washington

That moves east, we warm up a bit tomorrow, then quite a bit Tuesday/Wednesday. But Wednesday night another “ripple” is moving by, pushing lots of clouds inland. We’ll likely see some drizzle again Thursday morning, and some models even produce real showers Wednesday night and Thursday A.M.

By Saturday, a warm ridge is developing to our west (zig-zag line)… that’s sunnier, warmer, and back to “summer weather”. NEXT WEEKEND LOOKS SIGNIFICANTLY WARMER/SUNNIER THAN WHAT WE JUST EXPERIENCED

But just four days later, another cool trough is approaching. This is Wednesday, September 1st

What about rain? As of now, there’s no sign of a significant cool/wet spell. The ECMWF ensemble forecast for the next two weeks doesn’t show that either. Although there could be drips/showers here and there (possibly Thursday/Friday).

To summarize…

SUMMER ISN’T OVER, but if you want lots of hot weather, that’s not happening in the next 10 days.


This is EXCELLENT news! The last outbreak of lightning was back in the first few days of the month, and I don’t see any ahead. It appears we’ve only had one large (over 1,000 acre) fire develop in the past two weeks. That is the Fox Complex near Lakeview.

What’s ahead

  • Cooler plus higher humidity with occasional onshore pushes means less chance for huge fire starts, plus existing fires grow slowly
  • Westerly flow will continue send smoke east of the Cascades most of the time the next 10 days
  • I don’t see a setup where we get significant smoke west of the mountains over the next week and beyond
  • This weather pattern does not produce the dangerous easterly wind with its low humidity and high temps

The largest fires (or complexes) burning right now in Oregon

It’s good that we don’t have any sort of hot easterly wind event in sight…6 of those fires are burning on the west slopes of the Cascades!

I’ve said for years that what the weather does DURING fire season is far more important than the lead up in the spring. Remember we had our driest spring on record and most of Oregon is in severe drought. BUT, if we keep lightning away, humans don’t start fires, and we get occasional cooldowns/showers, we can make it through the rest of the season…fingers crossed

Chief Meteorologist Mark Nelsen

Hot Summer Temps Are Gone For At Least A Week

August 16, 2021

9pm Monday…

The heatwave ended today; a beautiful blue sky, temperatures in the 80s, and much lower relative humidity

That was after a sweaty six days of 90+ degree weather, peaking midweek with the 102 and 103

What’s Ahead?

  1. There’s no sign of a heat wave, or even 90 degree temperatures, in Portland during the next 7-9 days
  2. Other than a sprinkle/shower tonight & Tuesday morning, or a light weekend shower, the dry spell continues
  3. This next week will have that “the heat of summer is over” feel. Nights are getting longer and we’ll be cooler each morning
  4. Expect more cloud cover, especially mornings Friday through next weekend.
  5. Most likely we’ll turn warmer again during the last full week of the month (after the 24th)

Sunday was our 24th day at/above 90 in Portland. That’s the 3rd highest number of those hot days…after 2015 & 2018.

With two weeks to go in meteorological summer (June-August), many parts of the Pacific Northwest are on track for the hottest summer on record. That includes Portland, Salem, Eugene, Medford, Olympia, Pendleton, Burns, & Redmond. It’s interesting that North Bend isn’t even close. That’s because that location is dependent on warmer than normal ocean waters for a “hot summer”. And 1997 is the all-time high there due to the Super-Nino that year.

Of course we still have two weeks to go. This next week looks a bit cooler than average; starting with a mainly dry cold front passing overhead this evening. You’ve probably noticed the cool northwesterly breezes, clouds, and quickly dropping temps. This is associated with a cool upper-level system dropping down into Eastern Washington. Another one drops in over us or just to the east again around Friday. The result is more typical late summer weather; onshore flow plus cloud cover at times, then sunny periods. You can see the ECMWF forecast for the next week, showing a strong upper-level ridge (above normal heights in the higher atmosphere) in the Gulf of Alaska. That leads to lower than normal heights and upper-level troughing over Idaho. This is the pattern that gave us a dry and cool-ish spring at times.

But most models (including this one) show the ridging edging closer to us NEXT week. This is Sunday the 22nd through Sunday the 29th; a warmer pattern again, although not necessarily hot.

Both patterns (this week and next) are relatively dry; there’s no sign we have a late summer showery pattern setting up.

Enjoy the comfortable weather the rest of this week! Chief Meteorologist Mark Nelsen

Extreme Heat is Gone, but Hot Weekend Still Ahead

August 13, 2021

9:30pm Friday…

A quick post this evening. Here’s a summary:

  1. We are done with 100 degree temps, we’ll be in the mid 90s tomorrow, then lower 90s Sunday
  2. Humidity remains relatively high this weekend
  3. Smoke coverage will be similar tomorrow, if not a bit less, west of the Cascades
  4. Most of the smoke disappears Sunday afternoon; both at lower elevations and high overhead
  5. Heatwave #4 this summer will end up with 6 consecutive 90+ degree days

A thick layer of smoke kept us below 100 west of the Cascades today; we’ve been thinking all this week it might happen. Smoke modeling did pretty well!

This was our 22nd day at/above 90 degrees in Portland this summer.

But Salem just broke the all-time record. Today was the 35th day at/above 90 degrees. Those records go back into the late 1800s!

Strong high pressure remains nearby through Sunday, but increasing (cooler) onshore flow means temperatures drop a bit over the weekend.

HRRR smoke modeling has done relatively well the past two days, and it shows slightly cleaner air (at ground level) tomorrow morning

Then a 2nd push of marine air tomorrow evening really clears things out. By Sunday, just about all low-level smoke should be gone…we’ll see!

That’s it for tonight… Enjoy your weekend!

Chief Meteorologist Mark Nelsen


August 12, 2021

7:30pm Thursday…

You’ve just made it through ANOTHER 100 degree day in Portland. PDX hit 102 yesterday, and SO FAR has hit 103. That was the 6pm temperature. You see the entire metro area was in the 103-107 degree range. This would be our big summer heatwave…if it weren’t for the historic event back in late June that produced 108-116 temps at PDX. What a summer…

And the official numbers across the region

Off the map, a gusty northeasterly wind reached Bellingham, Washington today. That pushed the temperature to 100 degress…an all-time high! The airport there is located very close to the water so most afternoons a cooling onshore breeze keeps the extreme heat away. Not today; summer 2021 will be remembered for a long time all across the region. Notice a bit more onshore flow at the beaches = no heat there. A bit cooler than yesterday at Astoria and Tillamook.

For the hardcore weather geeks, I see the 850mb temperature on the afternoon balloon sounding over Salem was +25.8 degrees (C). That’s very near what used to be the all-time record…this is a hot airmass! There was about 1 millibar of easterly flow through the Gorge earlier today and some light easterly flow was blowing over the Cascades. That was just enough to warm us up a bit from yesterday. That easterly flow delivered a first batch of lowland wildfire smoke to the Portland metro area.

Here’s the current view from our Skyline Camera; not really a “postcard-perfect” moment in the Rose City is it? You can’t see more than about 15 miles; Troutdale and Gresham are out there…somewhere

Current AQI shows parts of metro area and Gorge into the “UNHEALTHY” category; not so bad up north at Longview and in the Willamette Valley.

I want to alleviate any renewed anxiety about us having another “SmokePocalypse” similar to last September

  1. There are no huge fires close by to produce massive volumes of smoke
  2. Flow goes westerly the next few afternoons = dense low level smoke shouldn’t get stuck in the valleys
  3. It’s not September, when it’s much easier to get inversions and smoke lingering
  4. Westerly flow returns at all levels of the atmosphere Sunday = much better later that day and next week

Check out the HRRR smoke modeling forecast. First, right now. Notice the colors (generally) match the Air Quality Index categories:

Then by tomorrow morning an even thicker surge of smoke has arrived at the eastern end of the Gorge. Really bad air Hood River, The Dalles, and farther east. But not much worse in Portland

Just in time, we switch to a light westerly flow tomorrow afternoon west of the Cascades. That pushes the thickest smoke over and east of the Cascades…at ground level. There will still be a sickly, yellowish sun overhead. Notice the model thinks the Tillamook forest fire will produce significant smoke; that seems unlikely.

By midday Saturday, a continuing (light) westerly flow is keeping most areas west of the Cascades in good shape, and west wind in the Gorge is helping a bit too. On Sunday I expect more westerly flow and even better conditions

Remember these are GROUND LEVEL forecasts, there will still be lots of smoke swirling overhead many thousands of feet up.

As for temperatures, the strong upper level ridge remains over us tomorrow and Saturday.

Then weakens with two cool upper-level troughs passing by both Sunday night and midday Tuesday. This returns us to a more typical morning clouds and afternoon sun routine. High temps drop back to around 80…much better!

By the way, Portland only dropped to 70 degrees this morning, which makes it an ALL-TIME RECORD WARM NIGHT FOR THE MONTH OF AUGUST. Salem now has a new record for the month too… at 69 degrees. The days of “you don’t need air conditioning in Portland” are over aren’t they? Take a look at this. The number of nights at/above 60 degrees at PDX for each decade.

Wow! What a change the past 10 years…of course in general a warming urban area is going to see warmer nights as the decades go on. But the past 10 years have been amazingly warm. Here’s the deal, clearly a large part of this IS the urban heat island. But some is our warming climate as well. I checked Salem, Eugene, Olympia (using both 60 and 65 as a cutoff) and can’t find a similar effect. Yes, nights are warming, but nothing so dramatic as what we’re seeing in Portland.

That’s it for now, I’ll be on at 8pm & 9pm (PDX-TV), and 10/11pm (KPTV). I’ll see you there.

Chief Meteorologist Mark Nelsen

Hottest Summer On Record Produces Another Heat Wave This Week

August 9, 2021

8pm Monday…

I was on vacation last week and part of the previous week, but back in the forecasting saddle this week. What has changed? It’s been hot, except for a brief cool down Friday-Sunday. And a “big” .03″ rain fell at PDX, ending our 51 day dry spell

Yesterday our own Jeff Forgeron (meteorologist on Good Day Oregon) married his best friend of 13 years under comfortable temperatures, low humidity, mainly sunny skies, and no smoke. A perfect afternoon for a “weather” wedding; Jeff nailed the timing, avoiding all the weather issues. Congrats Jeff & Katie! Here’s a nice pic of the weather team from Brian; the best team we’ve ever had!


I’ve just gone through the numbers, which are stunning:

  • #1 hottest summer on record at Portland, Salem, Eugene, Medford, Redmond, & Pendleton

This includes June 1st through August 8th. IF we have a cool 2nd half of August, that could knock us out of 1st place. For many stations, the previous “hottest summer” was 2015. Redmond’s previous hottest was 1968. Notice this includes BOTH stations where we’ve seen urban heating and others with little/no land change around the stations. This isn’t just about growing urban areas turning warmer (Example: Portland airport). We are living through a historically hot summer.


  • Portland’s 5 hottest summers? All recent (in order too): 2021, 2015, 2018, 2017, 2009
  • Salem has a longer record that goes back to 1893. Hottest years are the same: 2021, 2015, 2018, 2017, 2009
  • Salem has seen 31 days at/above 90 so far; by Friday the new record should be 35 days there.
  • Pendleton is a bit different. The 5 hottest: 2021, 1967, 1961, 1958, 2015


Portland has only seen 3.80″ rain since March 1st. That’s 5.5 months! If that happened every year, we wouldn’t have green trees all around us. That tells you all our vegetation is very stressed, and of course fire danger is extreme throughout the region. This is the driest we’ve ever seen during this period. BUT, down at Salem, over 6″ has fallen. Still well below normal, but “just” 10th driest. Pendleton has only seen 1.34″ during this time = driest on record like Portland.


Here we go again, just like in June (but not as intense); a strong upper-level ridge is developing just offshore. That means a dome of very warm air. Here’s the forecast for tomorrow; a 598dm ridge is highly unusual (again) at this latitude

Then by Thursday it flops in over on top of the Pacific Northwest. At this point 594dm heights cover much of the region. This is major heatwave territory from June through mid-August.

Now this model (WRF-GFS) quickly pushes a much cooler trough overhead Saturday and Sunday for dramatic cooling. Others keep the heat through Saturday; I think that’s a more likely outcome. Temperatures are forecast to peak around +25 to +27 (Celsius) Wednesday through Friday afternoons at 850mb. This is also major heatwave territory. Remember (until late June this year), the all-time high 850mb temp was +28.2. We will be close Thursday and Friday.

This will not be a heatwave with gusty easterly wind through the Gorge or into the western lowlands or OR/WA. That means two things. First, we won’t get as hot as we might get with a gusty east wind (106-108). And the coastline will remain reasonable, no hot east wind out there. Most likely even the north coast remains at/below 85 degrees this time around. You can see the weak/flat “thermal trough” straddling the western valleys and Cascades Thursday afternoon. This means no onshore cooling breezes, but no east wind either.

With all this in mind, we’re going for three days at/above 100 degrees Wednesday-Friday.

In reality, we could end up with just (1) 100 degree day. Why? First, Wednesday we might end up at “just” 98-99. Second, fire smoke is a big issue the 2nd half of the week. Even just a moderate smoke layer overhead could easily keep us in the 90s Friday. NASA’s GEOS-5 smoke modeling shows lots of smoke over the region Friday afternoon/evening

There are numerous small/moderate size fires burning in several complexes on the west slopes of the Cascades. We can assume they will burn more vigorously this week with heat and instability. As the upper-level ridge moves over/east of us Friday, that opens up southerly flow, bringing smoke north. Here’s the view this evening:

That’s it for now; I’ll be working most of this week. Make sure you follow me on Facebook and Twitter for more frequent updates there: Twitter: @marknelsenKPTV and Facebook @marknelsenweather

Chief Meteorologist Mark Nelsen