Unseasonably Warm Weather Hits Western Washington, Cooling Trend Expected by Weekend

Temperatures in the Olympic Mountains' thermal belt were already in the 70s overnight, with relative humidity dropping to between 15% and 25Photo byJulien DI MAJOonUnsplash

The Seattle area is experiencing a stretch of unseasonably warm weather as a strong upper-level ridge combined with low-level offshore flow drives temperatures higher than usual. The National Weather Service (NWS) reports that this heatwave will continue through Friday, with many locations expected to break daily temperature records.

Temperatures in the Olympic Mountains' thermal belt were already in the 70s overnight, with relative humidity dropping to between 15% and 25%. These conditions suggest that lower elevations will experience significant heat once daytime mixing begins. Some areas may also set records for the highest minimum temperatures.

On Friday, while coastal areas may get relief in the form of a cooling sea breeze, much of the interior lowlands will experience a near-repeat of today’s high temperatures.

However, the warm spell will be short-lived. By the weekend, the upper ridge will weaken, and onshore flow will increase, leading to cooler temperatures. The NWS notes that by Sunday, temperatures will return closer to seasonal norms. While there is a slight chance of thunderstorms in the Cascades on Saturday, confidence remains low at this time.