Hottest Weather of Summer Ahead

July 10, 2018

8pm Tuesday

Today was a fantastic day in my opinion…clouds to sunshine and temperatures right near seasonal averages.  The Willamette Valley ended up right around 80 degrees.

If you don’t like our mid-summer hot weather, find a cool place; it’s about to get hot west of the Cascades.  A sprawling upper-level ridge is already building this evening over the Pacific Northwest and more or less remains over us the next 7-10 days.


A long period of very warm to occasionally hot weather is likely Wednesday through the middle to end of NEXT week.

  1. Every day is likely to exceed 85 degrees, with temps as high as 95 either Thursday or Sunday/Monday.
  2. I think temps up to 100 or higher are unlikely at this point
  3. Overnight lows will be moving into the low-mid 60s at times…getting uncomfortable in the urban areas if you don’t have air conditioning
  4. Record highs are unlikely…all records through the 21st are at/above 101 degrees.

This one is interesting because it’s not a sharp ridge which gives us extremely hot weather and/or easterly downslope wind.  Instead it’s quite flat, indicating a large area of much warmer than normal temps.  Here’s the 500mb forecast from the ECMWF model ensembles (actual heights are the lines, anomaly is the color) for Thursday, Sunday, next Wednesday, and Saturday the 22nd.  No big, hot ridge, but abnormally high heights…seems like a lot of red across a good chunk of North America.

This slideshow requires JavaScript.

850mb temps peak out around +22 Thursday and 19-21 on ECMWF ensembles Sunday-Monday.  Without decent offshore flow it’ll be very tough to get above 95 degrees (good!).

Note the surface temp forecast for Portland from this model


These numbers are a good 8-15 degrees above average for our area.  If you are into water sports this is excellent news.  If you work for a paving company…well…October will eventually get here.  We can forget about precipitation because in this pattern even thunderstorms are hard to come by as high heights squash the convective stuff.  Not a single GEFS ensemble member produces even .10″ rain in the next two weeks.  The ECMWF is similar.


Of course if we’re going to get an extended very warm to hot stretch this IS the time to do it.  Notice that here in Portland the hottest time of the year is typically the 3rd week of July to the middle of August.


How about the coastline?  Can you escape the heat there?  Yes!  In this pattern we shouldn’t see easterly flow make it to the beaches so 65-80 is a good guess for the next week, depending on location and day

7 Day Coast Plus Cascades Summer

And the Cascade lakes will be an excellent place to be as well as anywhere else at/above 4,000′

7 Day Coast Plus Cascades Summer2

I would suggest Ape Cave or any other lava tube near Trout Lake or Bend…it’s in the 40s year-round in most of those cave since they follow the ground, not air, temperature.

On a “big-picture” note…unless something changes drastically in August, this is going to be our FIFTH warm/hot summer in Western Oregon and SW Washington.  I can’t find any other period in at least the last 100 years where we’ve seen such a stretch of abnormally warm weather.  2015 was the hottest summer on record here in Portland.


As mentioned in the past, this is one season in which we are seeing dramatic warming in our area…not so much in winter but in summer.  That doesn’t mean we can’t have a round of cool summers right around the corner, but the trend is definitely up.  That cool summer of 2011 seems a long way back now doesn’t it?

MarkSummer RecentYears

Chief Meteorologist Mark Nelsen