September is Here

September is the month where summer fades away and fall takes over.  Much like March where winter fades away and spring gradually takes over.


Notice that last fact.  Now compare it to the following graphic


Only 1 of the last 8 summers have not seen a 90 degree temperature in PDX.  That was the cool summer of 2010.  The last two Septembers we’ve even seen a 95 degree high in the first half of the month.  It’s also interesting to note that in both cases the next day it quickly dropped to around 80 degrees.  Just as in March it’s hard to keep daytime highs cold; it’s really tough to have several days of hot weather in September. 

This weekend will be similar with a couple days near (or above) 90 degrees Friday and Saturday, then a dramatic drop either Sunday or Monday as a cool trough moves by to the north.   That turns the dry and warm east winds back to onshore and cool.

The big picture over the next 10 days or so is for a strong upper-level ridge to linger just off the West Coast, keeping us mainly or all dry.  Most likely after the cool trough early next week we’ll see another fast warm up.  

The 00z GFS has no precipitation over us for the next 16 days, and the 12z ECMWF looks quite dry as well.  Here is the 10 day precipitation accumulation. ecmwf_tprecip_nw_41  A tenth of an inch over the mountains, and just about all of that was supposed to be this evening and tonight.  So basically no rain in the lowlands through the 11th of September.

Chief Meteorologist Mark Nelsen


25 Responses to September is Here

  1. WEATHERDAN says:

    80 in Salem at 1:30 PM going for 88. Next three days look to be 94 97 and 92. Then 80-85 Mon-Wed before more hot weather later next week. Our low under clear skies this morning was 50. Looks like low to mid 50,s the next few nights so some real good sleeping weather. Oh and on the subject of diurnal changes I don’t remember the exact date but in May of 1967 Pendleton had a low of 30 and a high of 92. That’s a change of 62 degrees. Peace.

  2. Tyler Mode in Battle Ground says:

    83 for me love this dry air.

  3. East winds have commenced here. 84 currently after a crisp 45 this am..

  4. Hal in Aims says:

    light breeze out of the east just started here…..

  5. Tyler Mode says:

    42 degrees this morning. Coldest since June 5th for me.

    • runrain says:

      43 deg running through Happy Valley Park at 6am this morning – brrr!! No cougar sightings, but did see a doe and fawn. And tons of rabbits as usual.

  6. High Desert Mat says:

    One can sure feel autumn approaching fast. Warm days with cool nights. At least here in the high desert. Once the sun goes down it cools pretty quickly now. Hence why I really don’t like hunting season. Cold nights and warm days.

  7. schmit44 says:

    9/3/2014 Oregon (All) Temperature Summary

    High:89 at BROOKINGS( 79 ft)
    Low: 66 at Brookings Airpor(459 ft)

    High:50 at CW7477 Lostine(7002 ft) & HOWARD Mt Howard(8150 ft)
    Low: 21 at DIMLKE (4726 ft )

    Largest Diurnal Change: 49 degrees
    Sand Creek (US 9 (73/24 ) (4525 ft )

  8. JohnD says:

    ‘Somehow this evening I found myself tapping videos of the winter storms from this past February. I’m a sucker for sentiment anyway–but what a great ride it was! Totally AWESOME! Never too early to start hoping for the coming season, right? And–especially with El Niño now at an apparent ebb–who knows!
    Anyway, right now pulling for a long, beautiful, warm and wonderful September-fall! Why not?!
    We’ll be at the Duck game Sat. amid late season 90’s!

  9. Tyler Mode says:

    My warmest August in my 18 years at my Minnehaha station.

    Mean temp of 72 degrees.

    The UHI was very pronounced during August.

    Average low for my BG station: 54.5

    Average low for my Minnehaha station: 58.6

  10. runrain says:

    Could be miserable at Autzen Saturday for the Ducks game. It starts at 3:30pm when temps are forecast to be in the low 90’s. In addition, looks like smoke from the Deception Complex fire will be pushed into the southern Willamette Valley, increasing the discomfort.

  11. mark says:

    I am wondering how long we will be locked in this ridge/trough pattern. It would seem that something would dislodge it after such a long time. All the charts I look at continue to hint at above normal temps and below normal precipitation for our area.

  12. W7ENK says:

    My largest diurnal change was at the beginning of August two years ago when we hit 100s in the valley — not sure of the exact numbers, I’ll have to look it up.

    I do recall that my smallest was 0.9 degrees that lasted almost 3 days during one of those fogversions a couple winters back.

  13. WEATHERDAN says:

    48 in Salem this morning. First morning low under 50 in 73 days. Now it’s back to warmth. In the 70,s today 80,s on Thursday and 90,s for Friday and Saturday and still close to it for Sunday. Then a brief cooldown and then another quick warmup. Before all is said and done Salem should windup with more than 30 days over 90 and 80 days over 80. A feat last done in 1967. FZ LVL dropped from 14.0 to 9.9k in only 12 hours. The NW winds were really blowing last night. Still the front was dry, at least in Salem. Anyway Summer isn’t done just yet so you snow lovers will have to wait for awhile. However by mid month it looks like the Midwest will see some highs only in the 50-55 degree range so Autumn is approaching. Go Ducks! Peace.

  14. Tyler Mode says:

    My low was 46 around 4:30 this morning. Apparently some clouds moving in now as my temp is up to 50.

  15. schmit44 says:

    9/2/2014 Oregon (All) Temperature Summary

    High:95 at ILLINOIS VALLEY(1389 ft)
    Low: 66 at RED MOUND(1753 ft)

    High:53 at MT HOOD TEST SIT(5400 ft)
    Low: 27 at Horse Ridge (US (4160 ft ) & KIRK (4519 ft ) & DIMLKE (4726 ft )

    Largest Diurnal Change: 56 degrees
    FOSTER FLAT (86/30 ) (5000 ft )

    Heaviest Rainfall:
    0.12″ at WANDERER’S PEAK(4350ft)

    • schmit44 says:

      Every year (usually in September) some of the mesowest stations in the high desert get those rare days with diurnal changes of 60 degrees or more. Today Foster Flat was 86/30. Look for the largest diurnal changes of the year these next 4 days in that area. The largest I have seen was 91/24 at Cabin Lake back in 2011.

    • Tyler Mode says:

      I love those type of days! My largest diurnal range at my BG station is 52 degrees on September 13th, 2012.

      After a low of 42, the high jumped to 94!

      The previous day was 38/85.

      I also had a 44/94 on the 17th of that month.

      For the smallest at my BG station:

      January 16th, 2011. A high of 55.9 after a low of 53.6. A range of just 2.3 degrees. BORING!

    • My largest diurnal change is 51° on 9-21-09

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