Another hot day on tap, but cooler weather is in sight

Another hot day on tap, but cooler weather is in sight
A sunbather takes advantage of the hot weather at Green Lake on Sunday.
SEATTLE -- Monday will bring a third-straight day of warm-to-hot temperatures in the Puget Sound area, but the heat will start easing a bit on Tuesday.

An excessive heat warning remains in effect until 10 p.m. Monday for the area that includes Seattle, Tacoma, Everett and Bremerton. A heat advisory is in effect to 10 p.m. for the southwest interior.

However, while Monday is shaping up to be toasty, it's not looking as toasty as the mid 90s we saw over the weekend. The air mass is still quite hot, but we've lost the additional heat generating power of the easterly winds off the Cascades. Also, a little trickle of marine air made it into the interior overnight, allowing low temperatures to drop into the upper 50s and low 60s in some spots. At 11 a.m., Sea-Tac was running 15 degrees behind Sunday's pace.

On the other hand, places where the marine air wasn't as successful in reaching are closer to 6-9 degrees behind the weekend pace. Thus, we are still expecting highs in the upper 80s to low 90s Monday around the Western Washington interior. (The daily record of 98 for Seattle is safe, though.)

Along the coast, it's another world, with persistent low clouds and temperatures stuck in the 60s. The Olympic Peninsula and far north are a pleasant midpoint with temperatures expected to reach the mid-upper 70s.

The marine air begins to take a better foothold against the hot air Monday night, meaning Tuesday will be even cooler, with perhaps brief morning clouds then sunshine with highs around 80.

By Wednesday, the heat wave is vanquished as the marine air triumphantly and emphatically rolls all the way inland to the Cascade foothills. That will mean a big switch to a mostly cloudy day with areas of drizzle and highs only in the upper 60s to mid 70s. Long range models hint that we'll remain in a cloudier and cooler pattern through the weekend.

Some interesting heat wave statistics:

This year marks only the fourth time in Sea-Tac history that we will reach 95 in two separate heat waves, having reached 95 on Saturday and July 8.

  • 1967: August 16 (98) and August 28 (95)
  • 1978: July 22 (95) and August 8 (95)
  • 1988: July 19-20 (95, 95) and September 2 (98)
  • 2010: July 8 (95) and August 14-15 (95,96)

(In 1977, there was a three day stretch of 95+ degree weather from Aug. 10-12, then a few days' slight cooling before it rebounded back to 96 in Aug. 17. I counted that as the same heat wave and not as one of the four in this statistic.)

This heat wave also at least has slight potential to be just the fourth time we have reached 95 or better for three consecutive days:

  • 1977: August 10-12 (95, 95, 96)
  • 2006: July 21-23 (97, 96, 95)
  • 2009: July 28-30 (97, 103, 96)