Isle Royale weather in September 2025

Expect 63°F daytime maximum temperatures in the shade with on average 6 hours of sunshine per day in Isle Royale in September. Check more long-term weather averages for Isle Royale in September before you book your next holiday to Michigan in 2025/2026.

  • 63°F maximum daytime temperature in September in Isle Royale63
    63°F max day temperature
  • 6 hours of sunshine per day
  • 13 days with some rainfall in September in Isle Royale13
    13 days with some rainfall
  • 45°F minimum night-time temperature in September in Isle Royale45
    45°F min night temperature
  • 13 hours of daylight per day in September in Isle Royale13
    13 hours of daylight per day
  • No heat & humidity in September in Isle Royale0
    No heat & humidity
  • 3.4 inches monthly rainfall in September in Isle Royale3.4
    3.4 inches of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Isle Royale5
    5 (Moderate) UV index
  • 54°F sea temperature in September in Isle Royale54
    54°F sea temperature

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The September weather guide for Michigan (Isle Royale) 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)  |  Imperial (°F)

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How warm is it in Isle Royale in September?

Daytime temperatures usually reach 63°F in Isle Royale in September, falling to 45°F at night.

How sunny is it in Isle Royale in September?

There are normally 6 hours of bright sunshine each day in Isle Royale in September - that's 44% of daylight hours.

How warm is the sea around Isle Royale in September?

The average sea temperature around Isle Royale in September is 54°F.

Does it rain in Isle Royale in September?

There are usually 13 days with some rain in Isle Royale in September and the average monthly rainfall is 3.4 inches.

Isle Royale September sunrise & sunset times

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

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 06:12 19:35
Monday, 15th September 2025 06:32 19:06
Tuesday, 30th September 2025 06:53 18:35

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