Washington State weather in September 2025

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

  • 21°C maximum daytime temperature in September in Washington State (Seattle)21
    21°C max day temperature
  • 7 hours of sunshine per day
  • 9 days with some rainfall in September in Washington State (Seattle)9
    9 days with some rainfall
  • 11°C minimum night-time temperature in September in Washington State (Seattle)11
    11°C min night temperature
  • 13 hours of daylight per day in September in Washington State (Seattle)13
    13 hours of daylight per day
  • No heat & humidity in September in Washington State (Seattle)0
    No heat & humidity
  • 49 mm monthly rainfall in September in Washington State (Seattle)49
    49 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Washington State (Seattle)5
    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.

Top Washington State destinations

Below are average maximum temperatures at popular countries, regions and places in Washington State in September. Select a holiday destination to see more weather parameters.

All Washington State destinations

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

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How hot is it in Washington State in September?

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

How sunny is it in Washington State in September?

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

Does it rain in Washington State in September?

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

Washington State September sunrise & sunset times

Browse the sunrise and sunset times for Washington State in September 2025. Select a month to view Washington State sunrise and sunset times for the next 12 months. The Washington State sunrise and sunset times shown below are for Seattle.

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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