Western WA on deck for rain, ‘unseasonably cool’ weather after brief heat wave

After some recent hot days, are you ready for some rain? Rain is in the forecast for later this week, with unseasonably cool high temperatures struggling to reach 70 degrees.

What is driving this rather dramatic change in the weather is a North Pacific weather system that is entraining leftover moisture from former Tropical Storm Henriette, which passed well north of Hawaii. This former tropical system will help “juice up” the North Pacific weather system as it moves into the Pacific Northwest late this week.

The wettest day looks to be Friday. Current forecasts predict North Sound lowland rain amounts in the 0.5-1.5 inch range, with the mountains receiving upwards of two or more inches of rain — a nice summer soaker.

So far this year, it has been exceptionally dry. As of mid-week this week, Seattle-Tacoma Airport (SEA) is more than 6.5 inches of rain behind average. Everett-Paine Field has a rainfall deficit of more than 12.5 inches, Olympia is more than 9 inches below average, and the usually wet Forks on the north coast is well more than 22 inches behind for the year. Nearly all of the state is categorized as being in the moderate to severe drought category, according to the U.S. Drought Monitor.

With rain comes relief to the region

The rain will bring several benefits. Gardens, yards, and more will soak in nature’s irrigation. The rain will also wash away the smoke from the Mason County wildfires that invaded the region this week. The rainfall should also dampen the Mason County fires and ease local wildfire conditions, at least for a time.

The rain also brings some downsides, though. Despite the brief rainfall a week ago, oil buildup on roads remains. Oil and water do not mix, meaning wet roadways have a greater potential to be slicker than usual. Take it easy on the roads and allow plenty of room with the car ahead of you.

Another downside is the burn scar from the 2022 Bolt Creek wildfire along the Stevens Pass Highway. A sufficient amount of rain in a relatively short period can create mudslides. Crews will be watching this potential situation.

Some are asking, does this wet August weather mean the end of summer? Not yet! After this weather system tracks inland, higher pressure aloft is expected to build over the Pacific Northwest, leading to a drying trend this weekend and a return of some sunshine. By next week, high temperatures are expected to warm back into at least the 70s, accompanied by even more sunshine that will likely persist through at least the end of the month.

So summer weather will not be over. Yet enjoy the short-lived cooler, wet August weather late this week, and if driving, take it easy on the roads.

Ted Buehner is the KIRO Newsradio meteorologist. You can read more of Ted’s stories here and follow him on X