Friday Harbor weather in September 2025

Expect daytime maximum temperatures of 18°C in Friday Harbor in September based on long-term weather averages. There are 7 hours of sunshine per day on average.

  • 18°C maximum daytime temperature in September in Friday Harbor18
    18°C max day temperature
  • 7 hours of sunshine per day
  • 9 days with some rainfall in September in Friday Harbor9
    9 days with some rainfall
  • 10°C minimum night-time temperature in September in Friday Harbor10
    10°C min night temperature
  • 13 hours of daylight per day in September in Friday Harbor13
    13 hours of daylight per day
  • No heat & humidity in September in Friday Harbor0
    No heat & humidity
  • 36 mm monthly rainfall in September in Friday Harbor36
    36 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Friday Harbor5
    5 (Moderate) UV index
  • 12°C sea temperature in September in Friday Harbor12
    12°C sea temperature

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The September weather guide for Washington State (Friday Harbor) 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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More about the USA

How hot is it in Friday Harbor in September?

Daytime temperatures usually reach 18°C in Friday Harbor in September, falling to 10°C at night.

How sunny is it in Friday Harbor in September?

There are normally 7 hours of bright sunshine each day in Friday Harbor in September - that's 53% of daylight hours.

How warm is the sea around Friday Harbor in September?

The average sea temperature around Friday Harbor in September is 12°C.

Does it rain in Friday Harbor in September?

There are usually 9 days with some rain in Friday Harbor in September and the average monthly rainfall is 36mm.

Friday Harbor September sunrise & sunset times

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

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:30 18:53
Monday, 15th September 2025 05:49 18:24
Tuesday, 30th September 2025 06:11 17:52

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