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Seattle, Washington Weather in September

Typical September in Seattle, Washington: days around 72°F, nights around 54°F, and the month cools about 6°F from early to late — based on 30-year climate normals (NOAA, 1991–2020), day by day below.

72°Faverage high

54°Faverage low

−6°Fearly vs late September

18°Fday-to-night swing

Traveling soon? See the live 16-day Seattle forecast →

Early, mid and late September in Seattle

The month split in three — the part of the answer a 30-row table hides.

Part of September	Avg high	Avg low
Early September (Sep 1–10)	74°F	55°F
Mid September (Sep 11–20)	72°F	54°F
Late September (Sep 21–30)	68°F	52°F

Daylight in Seattle during September

How much light the day gives you — useful for planning what you can still do after work.

13 h 21 minon Sep 1

11 h 43 minon Sep 30

−1 h 38 minlost across September

Day-by-day September normals for Seattle

Long-term daily averages (NOAA 1991–2020) — climate, not a live forecast. For the next 16 days, use the live forecast.

Day	Avg high	Avg low
Sep 1	75°F	56°F
Sep 2	75°F	56°F
Sep 3	75°F	56°F
Sep 4	75°F	56°F
Sep 5	75°F	55°F
Sep 6	74°F	55°F
Sep 7	74°F	55°F
Sep 8	74°F	55°F
Sep 9	74°F	55°F
Sep 10	74°F	55°F
Sep 11	73°F	54°F
Sep 12	73°F	54°F
Sep 13	73°F	54°F
Sep 14	72°F	54°F
Sep 15	72°F	54°F
Sep 16	72°F	54°F
Sep 17	72°F	54°F
Sep 18	71°F	53°F
Sep 19	71°F	53°F
Sep 20	70°F	53°F
Sep 21	70°F	53°F
Sep 22	70°F	52°F
Sep 23	69°F	52°F
Sep 24	69°F	52°F
Sep 25	69°F	52°F
Sep 26	68°F	52°F
Sep 27	68°F	51°F
Sep 28	68°F	51°F
Sep 29	67°F	51°F
Sep 30	67°F	51°F

September in Seattle through the years

Real photos taken in Seattle in September by Weathershot app users — different years, same month.

Sunny weather in Seattle, 72°F — September 21, 2021 (community photo) — ☀️ Sunny · 72°F · Sep 2021📷 Joe S.

Weather in Seattle, 59°F — September 18, 2022 (community photo) — 📷 59°F · Sep 2022📷 Jia H.

Cloudy weather in Seattle, 64°F — September 24, 2022 (community photo) — ☁️ Cloudy · 64°F · Sep 2022📷 ka tayboonvong

Weather in Seattle, 68°F — September 3, 2023 (community photo) — 📷 68°F · Sep 2023📷 craftchicksx3

Cloudy weather in Seattle, 52°F — September 30, 2023 (community photo) — ☁️ Cloudy · 52°F · Sep 2023📷 Joe S.

Clear weather in Seattle, 63°F — September 20, 2024 (community photo) — ☀️ Clear · 63°F · Sep 2024📷 Jamie I.

Partly cloudy weather in Seattle, 54°F — September 27, 2024 (community photo) — ⛅ Partly cloudy · 54°F · Sep 2024📷 Joe S.

Sunny weather in Seattle, 73°F — September 20, 2025 (community photo) — ☀️ Sunny · 73°F · Sep 2025📷 Natascha S.

More months: October · November · December · January · Live Seattle forecast

September elsewhere: Atlanta weather in September · Chicago weather in September · Denver weather in September · Miami weather in September · New York weather in September · Phoenix weather in September

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The September photos above were taken with Weathershot — it stamps the real weather onto your picture. Snap one in Seattle and it could land on this page.

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