Summer flashback? Thursday could hit 80 degrees

A sunny, warm -- and what was thought to perhaps be Seattle's last 80 degree day of the year -- on Sept. 11, 2017. Thursday might hit 80 again. (Photo: KOMO News)

SEATTLE -- What do 80 degrees in Seattle this year and zombies have in common?

They both have a penchant for coming back from the dead.

It sure looked earlier this month that after we hit 80 and 77 on Sept. 11 and 12th that it was probably it for warm weather. We've hit the mid 70s a few times since, but 80 degrees seemed like it was done. Or at least, I thought so.

But summer has decided that even though it's no longer on the stage, it can still burst back out from behind the curtain before autumn really gives it the hook.

A brief thermal trough will be building this week, peaking on Thursday. That will not only bring up some warm but turn our winds offshore for a day, adding in a little bit of extra warming oompf and sending highs up around 80 degrees. Had this still been actually summer, we'd be probably flirting 90 or so but since October is just a week away and we're losing daylight at roughly 4 minutes a day, it's 80 degrees that's now the challenging barrier to cross -- yes even through we were well into the 80s just three weeks ago. The record high for Thursday is 84 -- and that still seems safe -- but as a testament to how sporadic heat is in late September, the record high on Tuesday is just 78 while it's 89 on Wednesday.

The Northwest climate has a very slooowww transition from spring to summer, but the transition from summer to fall is lightning-quick as the jet stream begins its southward trek from Alaska in the late summer to traditionally parking over the Northwest by mid-late October.

And here it is by temperature (the brown/tan shaded area is the normal temperature range) -- note the slope is gradual for spring (left) and steeper in the autumn (right)

With that kind of steep decline, all we need is a week or so of a rainy or showery pattern, and by the time a ridge rebuilds, our average highs are a lot cooler.

But on the other hand - and I should have thought about this before declaring 80 degrees dead -- summer seems to always have a "parting shot" -- just when you think the heat is done and clouds and gloom are here to stay for a while, we get one last little punch of warm air as an encore. That appears to be the case again this autumn.

So those of you who had managed to somehow amid the hottest and driest summer on record managed to save up a personal sun holiday, Thursday is your final chance to use it (unless you're saving it for more winter-type activities) because after Thursday? We cool off rapidly and 65 becomes a challenge next week:

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