Record heat scorched Sea-Tac on this day in 2009 — Seafair returns with mixed weather

On July 29, 2009, the Seattle-Tacoma International Airport (Sea-Tac) recorded its first time exceeding 100 degrees — with a new all-time high temperature of 103. The previous record prior to that was 100 degrees set on July 20, 1994. The heat dome of late June 2021, though, completely erased that record with a new all-time high of 108 degrees.

July 29 also happens to be one of the driest dates in Seattle’s history. Referencing weather records dating back into the 1890s, measurable rain fell on this date only six times at the old Federal Building weather station and just five times at Sea-Tac, most recently last year. Measurable rain is defined as one one-hundredth of an inch or more.

This month is again a dry one. At Sea-Tac, only one hundredth of an inch has fallen, leaving a rain deficit of over 6 and a half inches so far this year. Usually quite wet, Forks on the north coast is an amazing 20 inches behind for the year.

Seafair week forecast

This is Seafair week. The Blue Angels and other air show participants arrive early this week, make practice runs Thursday and Friday, and perform during the weekend. The hydros also arrive early this week from the Tri-Cities and make their preparations during the week before racing over the weekend.

Warm weather with high temperatures in the 80s will greet the hydros, air show participants, and fleet week vessels along the Seattle waterfront. Late Wednesday and again Thursday, a few thunderstorms are expected to develop over the Cascades. On Thursday, lingering showers from those thunderstorms could slip west of the mountains across parts of the western interior, including the Puget Sound region.

Cooler temperatures are expected to accompany this weather pattern change, with highs climbing only into the 70s Thursday and into the weekend. Low-level onshore flow from the Pacific Ocean will also generate morning marine clouds each day that should give way to afternoon sunshine. The morning clouds may also alter air show performance levels – high vs. low shows – late this week and possibly into the weekend.

Dry conditions, lightning, could lead to wildfires

The Cascade Mountain thunderstorms, combined with the ongoing very dry conditions, could spark new wildfires thanks to lightning strikes. So far this summer, wildfire smoke has avoided much of western Washington.

However, the region has suffered wildfire smoke and poor air quality six out of the last eight summers, going back to 2017 when smoke spread south from British Columbia fires. Any local fire starts could change that.

Fortunately, the flow of marine air from the Pacific should keep air quality in good shape through Seafair weekend. The Seattle Mariners also return home from their current road trip to take on the surging Texas Rangers in a 4-game series starting Thursday through the weekend.

Weather conditions for Seafair, the Mariners’ home series, and any other outdoor events in the region should feel comfortable. Given the dry conditions, though, everyone needs to be very careful with any burning materials.

Ted Buehner is the KIRO Newsradio meteorologist. Follow him on X and Bluesky. Read more of his stories here.