Late-summer heat wave bakes Western Washington — but not for long

Most of Western Washington will be under a heat advisory until 11 p.m. Friday, with higher-than-average temperatures expected and potentially record-breaking highs for the second day in a row.

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On Thursday, both Seattle and Olympia broke their previous records set in 1973, with highs of 90 and 95 degrees, respectively. Parts of the Olympic Peninsula got even hotter, with Shelton and Forks hitting 97 degrees.

The National Weather Service expected the Friday high in Seattle to reach 89 degrees. If it were to reach 90 again, though, that would be just the fourth time Seattle has seen back-to-back 90-plus-degree days in September.

The normal high for Sept. 5 at Sea-Tac Airport (Seattle's official weather station) is 75 degrees. For Sept. 6, it's 74. That means Thursday's forecasted high of 91 would be 17 degrees above normal. The record high for Sept. 6 is 90. And if 90-degree highs in September sound wild to you, that's because they are. According to the NWS, Seattle has seen 90-degree temperatures in the month of September just 12 times in the last 40 years.

The good news is things will get back to relative normalcy — you know, in the context of our changing climate — this weekend.

High temperatures will be back in the mid 80s on Saturday and the upper 70s on Sunday with lows in the 50s.

Emeritus State Climatologist Nick Bond said heat waves this time of year do tend to be on the short side.

"Special weather conditions bring us heat," he explained.

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Those conditions include ridges of high pressure aloft and higher pressure at the surface east of the Cascades, which promotes winds from the east that move down from the Cascades, compress, and warm.

"This time of year, you really need those east winds to make it hot," Bond said. "And they don't come along all that often."

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That could also explain the lack of wildfire smoke this year, to some extent. Bond said that's also because the higher-elevation regions did OK in terms of precipitation this summer, keeping those potential hotspots moist and less susceptible to extreme fire. But part of it is also sheer luck.

"Oregon has had, certainly, their share of fires this summer, but we've kind of lucked out in terms of not getting that smoke delivered to us [by the wind]," he said.

Still, folks in Western Washington should stay cautious when it comes to fire safety over the next few days and weeks.

In addition to a heat advisory in the region, the National Weather Service has issued a red flag warning for parts of the Cascades and the Olympics. That will be in effect until late Friday night.

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National Weather Service meteorologist Matthew Cullen said that despite experiencing a cooler and wetter-than-normal August, fire season isn't over yet.

"The last few years, September has been problematic in that sense," Cullen said. "If we get warm and we get dry, it doesn't take much to start a fire to grow as you get the dry conditions and a little bit of wind with it."

And while luck may have been on Western Washington's side thus far, the National Weather Service and other local meteorologists are warning that we could see increasing wildfire smoke and haze over the next couple of days.