August 01, 2009

The Warmest July Ever at Sea Tac

The numbers are in, July 2009 was the warmest since record-keeping began at Sea-Tac Airport (late 40s).

The air above remains very warm above us right 850 mb--around 5000 ft-- it is 20C (68F)...which is much above normal. At low levels we have had weak onshore flow, bringing marine air and some clouds in the lower few thousand feet. A vertical profile at Sand Point is shown below. Notice the inversion at low levels, with temperatures increasing with height. The cool low-level air warms during the day and the inversion is slowly burned out in the morning hours...producing rapid warming. Temps remain warm in the mountains where they are above the marine layer.
In the lowlands away from the water temps will rise in the mid to upper 80s..with a few 90s. And very warm hiking weather in the Cascades. This hot period doesn't want to end.

There are some major changes suggested in the latest computer runs for the end of next week, when a strong upper low swings through....convection--thunderstorms--often come with such changes. We will see.


  1. as long as i can remember, the weekend of the hydros has always been HOT. But i sure hope we can get some thunderstorms just to cool off.

  2. Wasn't the first weekend of 8/95 unseasonably cool?

    This is usually the peak of the heat around here, though. I always find it interesting how quickly in August the weather starts to change. Right around the second or third week we start to get those random cool or rainy spells, usually weak and short-lived, but they start to pick up steam as the month progresses, then we get September, spectacular one week and crapola the next, usually on my birthday.

    As long as my tomatoes keep ripening...

  3. Cliff, did the previous station in Seattle (before Sea-Tac) have a warm or cool bias in relation to the airport? Or is that known?

    I ask because as I'm sure you know, July 1941 was the warmest July on record and about a tenth of a degree warmer than last month. Of course, the average maximum temperature that month was lower than July 2009 - it was the minimum temperatures that were higher enough to overcome that difference.

    August 1967 remains the warmest month ever in Seattle, either at Sea-Tac or otherwise. I'll have to look at the pattern for that month - it featured twelve straight days of 84+ highs (the current record) from August 9-20, and the lowest high temperature of the month was 72. The low temperatures that month only dipped below 55 once (52 on August 8). The month as a whole had an average high of 83.7, an average low of 58.4, only 0.02" of rain, 0 heating degree days, and 197 cooling degree days (normal for an entire summer is 173).

  4. Yep, the 1995 hydro races were run in a cold drizzle. I was in the hospital while my wife was in labor. We had gone in Saturday evening. He was born on Monday morning.

    I remember that weekend very well.

  5. THUNDERSTORMS?!?!?! Don't tease like that, Cliff! I know, I know, you said "we will see..." -- but I grew up in Connecticut, and I MISS THUNDERSTORMS. So every single thunderclap is a treasure, and if we get some real storms out here...??? I might just explode from glee :-D

  6. Real Dry. Red Flag warning in the mountains and I see a fire burning on the east slope of the Olympics. Makes for a real red sunset. I hope they can control it.

  7. Cliff speaks of some major changes on the way beginning next weekend or so. I noted yesterday that both the CPC 6-10 and 8-14 Day Outlooks were trying to push a little cooler and wetter weather into extreme western Oregon, and a bit into WA. But the updated CPC August outlook for WA showed a pretty good chance for above normal temps. Very curious to see how this month goes . . .

  8. Well I don`t know about calling it 'major changes'. It`s looks just a little cooler for end next of next week highs off the WRF showing low 70`s with possible cut-off low coming into our region. So maybe more like 'small, but noticeable changes' to our weather for the work week.

  9. dawsonct and JorPet, here's the data to support your memories:

    Saturday, August 5, 1995: High 69, Low 57, Trace of Precipitation
    Sunday, August 6, 1995: High 63, Low 55, 0.35" Precipitation

    So, yes, a little cooler than normal, but nothing cold. Although the high of 63 on August 6, 1995 is still a record for the coolest high temperature on that date.

  10. i was in pullman in 1995, so it was hot there.... i just wish it would cool SOME... i feel so limp and the heat is giving me a headache.

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