Meteorological Fall Is Here: What To Expect In September & Beyond

SEATTLE —A push of marine air Thursday morning granted Western Washington a small taste of what's ahead as summer heads into the home stretch toward autumn. While the autumnal equinox is three weeks out, in a meteorological sense, fall is already here — but it could be a while before things take a turn for the brisk.

Differing from astronomical seasons, meteorologists and climatologists measure the periods in three-month cycles, based on their annual temperature patterns. In the Northern Hemisphere, meteorological fall covers September, October, and November. Like meteorological spring, fall is classified as a "transition season" between the warmest and coldest months.

Though climate predictions favor a hotter than usual September, the weeks ahead should be a far cry from the heat that persisted over the latter half of summer. According to the National Weather Service, Seattle's mean temperature for July and August was just under 70 degrees, making for the third-warmest on record. Meteorologists said nine of the top 10 hottest July/August periods happened in the past decade.

Monthly outlooks from the Climate Prediction Center favor above-normal temperatures lingering through September and place equal odds for how things play out on the precipitation front.

Looking ahead to longer-range forecasts for the full September-November period, the Climate Prediction Center shows equal chances for a cooler or warmer fall for most of Washington, with a better shot and above-average rainfall.

AccuWeather's 2022 fall forecast predicts the Pacific Northwest will be among the nation's first regions to head into the wet season, with rain and high-elevation snow possible by early October.

In the nearer term, the National Weather Service expects temperatures to taper off after Friday, with afternoon highs topping out in the mid-70s Saturday, Monday and Wednesday while running a bit warmer Sunday and Tuesday.