A comfortable July so far, but heat wave #2 arrives early next week

9pm Wednesday…

Today was a bit hot…for the 2nd consecutive day we made it above 90 degrees in Portland. That’s the 7th day so far this summer


You see the typical cool beaches and very hot east of the Cascades in the daytime highs



Tomorrow should be cooler as the hot upper level ridge just to our east shifts farther away, plus a weak system passes by overhead. The combination of these two has started a “marine push” of cooler air through the Coast Range gaps and up the Columbia River. The result will be patches of low clouds tomorrow morning inland and temperatures remaining in the 80s. A stronger push tomorrow night makes for a refreshing day Friday; there’s a decent chance we don’t get above 80 degrees that day…quite nice! July has been near normal in our area, but very warm across a good chunk of the USA. Note that this graphic is a few days behind.


But we have a heatwave ahead folks! Next week will feature the hottest stretch we’ve seen so far this year, and I give it a 50/50 chance this could be the hottest of summer when we look back.


  • Comfortable weather returns the next 3 days
  • Sunday turns hot, about like today
  • For at least 3 days (Monday-Wednesday) temperatures will be up around 100, plus or minus a couple of degrees
  • There’s a decent chance we make it to 100 in Portland/Salem/Eugene
  • There’s a much smaller chance we make it to 105 in one of these I-5 cities.
  • We don’t expect an extreme heat wave

Why so hot?

A strong upper-level ridge builds right over the West Coast AFTER a cool system passes nearby tomorrow through Saturday. Over the past few days models have been in some disagreement on the strength of the ridging. Would it be a huge “heat dome” with upper level heights over 594dm at 500 millibars with high temps well above 100 degrees (ECMWF/GEM)? OR, just high heights with general ridging…high temperatures 90-95 degrees (GFS), nothing too unusual. Luckily models have come together much better today. The Euro has cooled, and the GFS has warmed. 500mb heights on Sunday are rising, very warm, but no big ridge over us.

Then on Monday afternoon heights have risen a bit more. A ridge is building over the Gulf of Alaska, and most of the USA is covered by a hot/flat ridge

By Wednesday afternoon the two have linked up into a hot ridge right through the Pacific Northwest. Heights around 591dm


850mb temps (temperature in Celsius around 4,000′) look like this right now over Salem from the morning/midday runs:

GFS ENSEMBLE AVG+17+20+20+20
GEM ENSEMBLE AVG+20+22+23+23

I based my forecast off +22 to +23 degree temps.


This tells me we’re not going to see a major/historic heatwave, but a more typical mid-summer event. 591dm heights oriented like this don’t produce a hot/gusty easterly wind across the Cascades and no models are showing that hot downsloping. Instead we’ll just experience a shutdown of the cooling onshore breezes for 2-3 days with the hot atmosphere overhead. That should push us up to right around 100 degrees Monday-Wednesday. Sometimes this setup (no dry east wind) can lead to relatively high humidity as small amounts of marine air seep into the I-5 corridor…we’ll see.

The heat next week will also ensure that July ends up as a warmer than normal month.

Enjoy the cooldown the next few days!

25 Responses to A comfortable July so far, but heat wave #2 arrives early next week

  1. Roland Derksen says:

    The clouds stayed here until about 2pm- brought in by a marine inflow this morning. This appears to be the coolest day for the next several days ahead. It will be intresting to see if we come close to the temperatures during the late July 2009 heat wave.

  2. Weatherdan says:

    74 at present. Looking for right around 80 today. Clouds parted around 1:15PM. My vegetable garden is real happy right now. Maybe not so much after next week. Still it’s better than last Spring. Peace.

  3. OC550 says:

    I’ve really enjoyed this summer’s weather so far, but I am not looking forward to next week’s temps. I hate extended heat waves.

    • Paul D says:

      The 2 or 3 day in a row 90+ days have been tolerable. Next week is going to be downright miserable

  4. Zach says:

    Unfortunately, the cooldown from this heatwave is going to be very gradual.

  5. Evan -- Cedar Mill says:

    There’s actually a decent chance we don’t hit 100 next week

  6. MasterNate says:

    What is the record number of 90 degree days in a row for PDX? This heat wave could be a challenger

  7. Evan -- Cedar Mill says:

    Kinda starting to doubt we even hit 100 next week.

  8. Roland Derksen says:

    Yes, this is still turning out to be a warmer than average July this year- although it’s quite a bit cooler than last July. I expect August will be the warmest month of the year.

  9. Zach says:

    The longest stretch of 100F+ consecutive days at PDX was in July 1941 where we had 5. We may be able to tie or exceed that by a day.

  10. Evan -- Cedar Mill says:

    Models are backing off somewhat

  11. Joshua Lake Oswego says:

    I don’t know if I would call 7-9 days at 90+ including 3 around 100 a typical mid-summer heatwave. Don’t we only average 11 or so 90 degree days per year? We’ll, we used to.

    • Anonymous says:

      the sentance “We’ll, we used to.” doenst make sence, it wouldav made more sence if you said “well we used to” but what u said makes no sence

    • Joshua Lake Oswego says:

      Autocorrect did that. It is supposed to be “well”. Thank you for noticing, Mr. or Mrs. English professor.

      • Gene says:

        Joshua, I thought you were very nice to not point out the completely incoherent reply, riddled with misspellings, from Anonymous as he attempted to chide you for your ONE spelling error!

  12. ocpaul says:

    I enjoy cool downs any time of the year!

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