September Starts With Record Heat + Fire Smoke

9am Thursday

Wednesday was so refreshing with some morning clouds, afternoon sunshine, low humidity, and no fire smoke.  At least west of the Cascades there was no smoke.  A different story in Central Oregon…yuck!  Check out the view from low earth orbit yesterday afternoon.  Bend and Redmond are down in that muck.

Today will be similar with another push of morning cloud cover followed by a quicker breakout to sunshine as northerly flow develops.  Enjoy the “cool” because the heat is coming back big-time.  First, a quick look at Summer 2017 since technically it’s over after tomorrow; September arrives Friday.

SUMMER 2017 WILL LIKELY TIE 2009 AS THE 2ND WARMEST ON RECORD.  June was warmer than normal, July was close to normal, and of course August has been a scorcher.


And what most of you probably noticed…this summer was far sunnier than normal.  In fact from June through August we saw less than half of our typical number of “cloudy days”.  That’s defined as 80% cloud cover or more for any one day.


It’s been drier than normal, in fact 2017 WAS THE DRIEST SUMMER SINCE 2003 IN PORTLAND.  That said, summers are almost always quite dry around here, so this time it’s just been a “little drier”

So once again we’ve had a hot summer, this is the 4th consecutive warm/hot summer in the Pacific Northwest.  As mentioned in an earlier post, our summers have been warming, and the warming is even more dramatic in some other western USA locations.  A quick check of Missoula, Boise, Salt Lake City, Reno and a few other cities show similar summer warming.    We’ll see if the trend continues the next few years.

As of this morning, we’ve seen 18 days at/above 90 degrees in Portland; I think there’s a good chance we’ll add 6-8 more before September finishes.

Now let’s look ahead, but the view isn’t a good one.  I enjoy warm to hot summer weather but this next week looks terrible.  Why?  I think we are going to have a 5-7 day episode of thick fire smoke combine with hot temperatures.  Yuck!

How hot is it going to get?  This is our current 7 Day forecast

All the ingredients are there for a rare 100 degree day in September Saturday, and possibly again Tuesday next week.  First, we have a strong upper-level ridge developing this afternoon.  It’ll look like this Saturday:


Then on Monday and Tuesday the ridge “sharpens” a bit (becomes more south/north oriented)

When the ridge is sharper, we tend to get strong offshore (easterly) flow.  That can lead to extreme heat situations in the warm season.  For example, when we hit 105 on September 2nd, 1988, we were in a similar situation.  That day we saw our warmest 850 millibar temperature ever recorded during a Salem weather balloon sounding.  It hit +28 celsius up around 5,000′.  You can see it in the balloon sounding climatology here:

Here’s the issue, models are showing the temperatures Saturday through Tuesday will be equal to that value…somewhere between +26 and +29 C.  If we were to get offshore wind flow any of those days, we could go over 100 in September for the first time in almost 30 years.  As of now it appears Saturday and Tuesday hold the “best” chance for that to happen.  But there’s one big “fly in the ointment” as they say…FIRE SMOKE.  For at least 5 days, starting Saturday, the wind flow will be from the south & southeast above the lowest few thousand feet.

There are many fires putting out huge quantities of smoke to our south and southeast, but there won’t be much low-level wind to get rid of smoke through that period.  As a result there is an increasing change we’ll have record September hot temperatures under a very dense layer of smoke this weekend and early next week.  The smoke could be as thick as what we saw with those Canadian wildfires back in early August.  That won’t be any fun, but it could put a big dent in our forecast temperatures; that’s the reason I didn’t go totally nuts with highs up around 105 either Saturday or Tuesday.  We may just stay in the 90s if the smoke is real thick.

Regardless, if our 7 day forecast is correct, or even 2-3 degrees too warm each day, the first 6 days of this September will be the hottest start to the month we’ve ever experienced!

The flip side to this is unusually cool weather to our east.  On a Facebook TV meteorologist group there has been some discussion of the unusually chilly middle/eastern USA.  One broadcaster in Oklahoma mentioned that this “cool” August is almost unheard of.  Interesting.

Chief Meteorologist Mark Nelsen

17 Responses to September Starts With Record Heat + Fire Smoke

  1. Paul D says:

    I’m noticing a trend in Mark’s blogs lately: nothing but bad news! It’s not Mark’s fault, but it is a trend that isn’t going to change soon enough.

    • I wonder what it will mean if the trend continues through the winter. Lots of 50 degree days and below-normal rain, or back-to-back snowfalls that will make the last winter’s snow seem like flurries.

  2. Dallin Burnett says:

    Your definition of summer seems a bit off. Isn’t September warmer than June? If summer has to be defined as three months, why can’t one month be the second half of June and first half of September?

    As for this weekend, I have a sliver of hope that we can hit 107 or above. Imagine that, our all time record high in September, like LA when they hit 113 in September a few years ago.

    • W7ENK says:

      It’s the distinction between meteorological Summer and astronomical Summer.

      Meteorological Summer runs June 1 to September 1, but IMHO it’s a really poor way to measure our Summers because it fails to take into account the roughly 6 weeks of seasonal lag in temperatures.

      Astronomical Summer runs from the Summer Solstice (June 21-ish) to the Autumnal Equinox (September 21-ish). While astronomically literal, this method still fails to account for seasonal lag, though because it runs 3 weeks behind meteorological Summer, it’s a slightly more accurate method.

  3. oldwxwatcher says:

    I well remember that 105° on September 2, 1988. I spent a good part of the afternoon reaching/crawling under the dashboard of a friend’s new Honda CR-X, which was parked in my driveway, installing a new radio and speakers. I was well-done by the time I finished the job. No forest fire smoke then, thankfully.

  4. Roland Derksen says:

    I haven’t counted up my statistics for this summer yet (because for me summer doesn’t end til the equinox date) but here’s a couple of things: This will be my driest July-August period on record with just 0.50 inches. (previous record in 2006 with 0.83 inches). As far as the driest summer on record goes (for June 21-September 20) it’s got a good chance to make it; My current record holder there was Summer 1993 with 2.83 inches. One last thing; September 3,1988 was my only time for seeing a 90+ temperature in that month, but we have a good possibility of either tying or exceeding it next week.

  5. David Foster says:

    We also had one of the rainiest seasons ever, I believe records were set in October and November. The weather is always changing, I like it though except for the smoke.

  6. coldest to hottest
    something wacky going on
    interesting times

  7. Christiana says:

    Any idea how long the hot weather will last?

    • Paul D says:

      WAY too long!!! 😦

    • Garron 1/3 of a mile from the Hillsboro airport says:

      Well, we got a pretty good shot at the middle of October through late April being cool. But you never know, mother nature has the dice, and she’s rolling HOTTT right now!!!

  8. Jason Hougak says:


  9. JJ78259 says:

    We are going to see beautiful mid 85 degree weather next week! Lows into the mid 60’s very cool indeed!

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