Seattle weather in September 2025

Expect 21°C daytime maximum temperatures in the shade with on average 7 hours of sunshine per day in Seattle in September. Check more long-term weather averages for Seattle in September before you book your next holiday to Washington State in 2025/2026.

  • 21°C maximum daytime temperature in September in Seattle21
    21°C max day temperature
  • 7 hours of sunshine per day
  • 9 days with some rainfall in September in Seattle9
    9 days with some rainfall
  • 11°C minimum night-time temperature in September in Seattle11
    11°C min night temperature
  • 13 hours of daylight per day in September in Seattle13
    13 hours of daylight per day
  • No heat & humidity in September in Seattle0
    No heat & humidity
  • 49 mm monthly rainfall in September in Seattle49
    49 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Seattle5
    5 (Moderate) UV index

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The September weather guide for Washington State (Seattle) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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How hot is it in Seattle in September?

Daytime temperatures usually reach 21°C in Seattle in September, falling to 11°C at night.

How sunny is it in Seattle in September?

There are normally 7 hours of bright sunshine each day in Seattle in September - that's 57% of daylight hours.

Does it rain in Seattle in September?

There are usually 9 days with some rain in Seattle in September and the average monthly rainfall is 49mm.

Seattle September sunrise & sunset times

Browse the sunrise and sunset times for Seattle in September 2025. Select a month to view Seattle sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:28 18:49
Monday, 15th September 2025 05:47 18:21
Tuesday, 30th September 2025 06:08 17:50

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