Surge of hot summer weather to come before autumn equinox

Labor Day Weekend 2024 has come to an end and many schools are finally resuming classes this week. Yet, summer weather is not over.

Days are getting shorter by more than three minutes per day with sunsets now arriving before 7:45 p.m. The autumnal equinox is just a few weeks away on Sept. 22. But until that date, the summer season continues.

Onshore flow from the Pacific Ocean returned marine clouds to Western Washington on Labor Day. But higher pressure aloft building over the region will permit the sun to return with warmer temperatures on Tuesday. The low-level onshore flow is expected to switch to offshore Wednesday, resulting in even warmer summer-like temperatures for the rest of this week.

More on the remaining summer season: Is summer over in Western Washington? Nope, a bit more is coming this week

High temperatures Tuesday will range from the mid-60s into the 70s, and warm into the 70s Wednesday. By Thursday and Friday, areas away from shorelines will have highs rise back into the 80s, even cracking the 90-degree mark south of the Puget Sound. Shoreline areas will have high temperatures in the mid-60s to 70s. Average high temperatures for the western interior in early September are in the lower to mid-70s.

Looking further ahead, no significant rainfall is anticipated with more summer-like temperatures heading into mid-September. Despite the wet week in the latter part of August, the latest U.S. Drought Monitor continues to show much of the western interior and Cascades is in either abnormally dry or moderate drought conditions.

August did turn out to be wetter than average. Forks was among the wetter locations with nearly five inches of rain reported, just over two inches above average. Bellingham got just over 2.5 inches of rain during the month, approximately 1.5 inches above average.

From central Puget Sound southward, including Seattle Tacoma International Airport (SEA) and Olympia, 1.5 inches of rain fell, about one-half to two-thirds of an inch wetter than average. For the year though, that same region remains between one and four inches of rain behind average.

Overall, August’s average temperatures (highs and lows) across Western Washington were a mixed bag. The coast and Olympia were warmer than average with Forks nearly 2.5 degrees above average. In contrast, Sea-Tac and Bellingham were less than one degree below average.

Sept. 1 marked the start of “meteorological fall.” Yes, the astronomical summer season continues until the autumnal equinox. Yet, the meteorological fall months of September, October and November better represent what the time of year feels like.

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For instance, the months of December, January and February mark “meteorological winter” – the coldest months — while June, July and August are the hottest months of the year and are “meteorological summer.”

Astronomical fall, commonly called the first day of fall, starts with the autumnal equinox and runs through until the winter solstice, or the shortest day of the year in late December. So, the difference between the astronomical and meteorological seasons simply comes down to the start and end dates.

If it seems that summer has been running longer in recent years, your sense would be correct. Studies have shown that since the 1950s, the summer season has now, on average, been three weeks longer globally, starting earlier in the spring and extending into fall. In 2022, high temperatures soared into the 80s on Sunday, Oct. 16 — the warmest ever for so late in the year, serving as yet another example.

Regardless, fall is just around the corner as the days get shorter and nights become longer, which means cooler, wetter weather is near. In the meantime, enjoy what summer weather remains!

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