Weather Blog

Moon landing? July 20th also marks important Seattle weather date

Moon landing? July 20th also marks important Seattle weather date

Forty years ago today, man walked on the moon. Those watching the 25th anniversary coverage of the event in 1994 were likely sweltering or finding shelter some place air conditioned as it was a memorably hot day.

I was at Alki Beach that day and can attest that for anyone landing on the steaming sand barefoot, it was one small blister for man, but one giant yelp heard by all of mankind.

July 20, 1994 is the only date in the entire record book at Sea-Tac Airport where the temperature has reached triple digits.  The high hit 100 degrees (actually, it hit 99.9 and was rounded up, so technically speaking, we've never hit 100.)  In this sense, Seattle makes a fantastic Fahrenheit scale since our all time record high is 100 and the all time record low is 0.  (Later this week, I'll blog about the crazy Fahrenheit scale and how it was created.)

The 100 degree anniversary is poignant this year because there is a passable chance it could be the last year that feat is celebrated as the only time it's happened.

The entire West Coast remains locked in a very toasty weather pattern with the air mass just about as hot as it can get, aided by a very strong ridge of high pressure anchored across the West. (When you hear Phoenix is having their 5th warmest July ever so far, and nine of the past 10 days have been over 110, you know there's plenty of heat out there.)  And now we're heading into the peak of the heating season anyway, which is late July/early August around here.

A testament to how hot the air mass is on its own is the fact that Seattle hit 90 degrees on Friday with no easterly wind component -- those warm winds that sink and compress when they roll down the Cascades are typically a needed ingredient to hit 90 around here.

It looks like Seattle might hit 90 again on Tuesday but it's next weekend where forecasting models think we really might turn on the afterburners. A number of forecasting models show the perfect combination of this still very hot air mass, now combining with a very strong east wind.  Highs Saturday and Sunday in the greater Seattle area could get into the mid-upper 90s, which would start setting records.

But there are a few hints on some of the models that if it comes together as advertised, Seattle has at least a passing chance of hitting 100 sometime late this weekend or early next week.

Now, that said, as usual, there are caveats. There are a few models -- not the majority -- that show instead a weak trough passing through, and stalling over the area over the weekend. That would keep us warm (air mass, still hot) but not record warm. So the 90+ forecasts need a bit of an asterisk right now, but it is still the majority, so it's what we're going with.  Even the main U.S. forecast model has been sort of toying with what to do, flipping back and forth a bit between a high of 97 and 86 for the weekend just on the Monday morning forecast runs alone.

But suffice to say, we don't expect any cool weather any time soon, with generally above-to-well-above normal temperatures the rule for at least the next 10 days. So, keep those flip-flops handy if you're heading to Alki. Trust me :)