Boise weather in September 2025

Expect 25°C daytime maximum temperatures in the shade with on average 10 hours of sunshine per day in Boise in September. Check more long-term weather averages for Boise in September before you book your next holiday to Idaho in 2025/2026.

  • 25°C maximum daytime temperature in September in Boise25
    25°C max day temperature
  • 10 hours of sunshine per day
  • 4 days with some rainfall in September in Boise4
    4 days with some rainfall
  • 8°C minimum night-time temperature in September in Boise8
    8°C min night temperature
  • 12 hours of daylight per day in September in Boise12
    12 hours of daylight per day
  • No heat & humidity in September in Boise0
    No heat & humidity
  • 19 mm monthly rainfall in September in Boise19
    19 mm of monthly rainfall
  • UV (maximum) index 6 (High) in September in Boise6
    6 (High) UV index

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The September weather guide for Idaho (Boise) 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 Boise in September?

Daytime temperatures usually reach 25°C in Boise in September with no heat and humidity, falling to 8°C at night.

How sunny is it in Boise in September?

There are normally 10 hours of bright sunshine each day in Boise in September - that's 80% of daylight hours.

Does it rain in Boise in September?

There are usually 4 days with some rain in Boise in September and the average monthly rainfall is 19mm.

Boise September sunrise & sunset times

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

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 06:09 19:19
Monday, 15th September 2025 06:25 18:54
Tuesday, 30th September 2025 06:42 18:27

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