9pm Tuesday...

Since I last posted, we've seen August give way to September. Labor Day Weekend has come and gone too, a nice "end to summer" with abundant sunshine but no hot weather.

Of course, meteorologically we just finished summer which runs from June to August. In Portland, Summer 2021 was just barely edged out by a slightly hotter Summer 2015. By 0.1 degree! Basically, it was tied with 2015 for hottest summer on record at PDX.

Summer So Far Two Months.png

In Salem, Eugene, Medford, & Redmond it was the hottest on record. As I've mentioned many times, Salem's climate record is excellent, going back to the late 1800s. This summer was a scorcher!

This was our 9th consecutive warm/hot summer; of course, not all of those were "hot". Last year is a good example, just a bit warmer than average. 2012 was the last time we had a "cool" summer, mainly due to a very cool June. But 2015, 2018, & 2021 have been blazing hot. Portland has seen (so far) 24 days at/above 90 degrees. That's at the higher end, but we've seen more in 2015 and 2018.

90 Degree Days Summer Heat.png

Salem has seen 39 days that warm; a new all-time record there. Eugene also set a record...41 days at/above 90 degrees!

Of course, the drought continues... Portland has only seen .05" rain in just under 3 months. And the six-month period from early March through early September is the 2nd driest six-month stretch on record. Summer & early fall 1987 were slightly drier.

Spring Rain Dry.png

This means we are seeing another very dry "water year". By the way, a water year is a term used throughout the Western USA. Since most precipitation falls in the cold season (straddling two calendar years), it makes sense to look back at wet seasons separately, which means starting the "water year" on October 1st each year and ending September 30th. We've got three weeks left this year. Right now, it's the driest since the 2000-2001 drought year...in Portland.

Rain WaterYearPDX.png

We haven't seen a wet year since 2016-17. Of course, we could easily pick up 2" rain the 2nd half of September, but even then it would be a much drier than normal year. Typically we get about 36" in Portland each year.

Do we have any rain ahead? Not really, at least nothing significant through mid-month. A weak system drops a few showers tonight, then mainly or all dry through at least next Tuesday/Wednesday. Take a look at the ECMWF ensemble forecast chart for the next two weeks. It shows 24 hour rainfall. Each thin horizontal line on upper part of chart shows one of the 51 ensemble members. Time goes from now (left) to two weeks out (right).

ECMWF Ens Precip.png

Notice almost no members produce .10" or more through the middle of next week, instilling high confidence that we'll be dry through the 15th. But you'll also notice around the 18th or so a lot of ensemble members say we could actually see rain. I'm not saying this is the case, but every few Septembers we get a big soaking the 2nd half of the month. In fact 3 of the past 4 Septembers we've picked up at least 2" rain during that time.

It would be wonderful (and mainly finish the fire season) if we could get 2" of rain in valleys plus 4" in mountains the last ten days of the month.

One more note, it's also obvious that we're making a turn toward more typical (cooler) September temperatures starting Thursday. The same morning ECMWF model ensembles show temperatures consistently in the 70-80 degree range the next 10+ days.

ECMWF Ens Temps.png

Summer is over...but warm early fall weather is here for awhile longer

Chief Meteorologist Mark Nelsen

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