The Brief

Fall officially starts in Seattle with the autumnal equinox on Sep. 22, 2025.

Meteorological fall began on Sep. 1, based on expected seasonal temperatures.

Cooler weather is expected in Seattle after this week, aligning with the equinox.

SEATTLE - While the weather is usually a telling sign, many in the Pacific Northwest are anxiously waiting and asking, when does fall officially start in Seattle?

The start of fall is signified by the autumnal equinox , which is on Monday, Sep. 22, 2025 in the Northern Hemisphere. Also known as astronomical fall, it starts once the Sun's center passes through Earth's "celestial equator," or an extension of the equator line if it stretched into space.

However, meteorological fall began on Sep. 1, indicated by the Earth's temperatures

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