Decatur weather in September 2025

Expect 79°F daytime maximum temperatures in the shade with on average 8 hours of sunshine per day in Decatur in September. Check more long-term weather averages for Decatur in September before you book your next holiday to Illinois in 2025/2026.

  • 79°F maximum daytime temperature in September in Decatur79
    79°F max day temperature
  • 8 hours of sunshine per day
  • 8 days with some rainfall in September in Decatur8
    8 days with some rainfall
  • 55°F minimum night-time temperature in September in Decatur55
    55°F min night temperature
  • 12 hours of daylight per day in September in Decatur12
    12 hours of daylight per day
  • Low heat & humidity in September in DecaturL
    Low heat & humidity
  • 3.2 inches monthly rainfall in September in Decatur3.2
    3.2 inches of monthly rainfall
  • UV (maximum) index 6 (High) in September in Decatur6
    6 (High) UV index

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The September weather guide for Illinois (Decatur) 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 hot is it in Decatur in September?

Daytime temperatures usually reach 79°F in Decatur in September with low heat and humidity, falling to 55°F at night.

How sunny is it in Decatur in September?

There are normally 8 hours of bright sunshine each day in Decatur in September - that's 65% of daylight hours.

Does it rain in Decatur in September?

There are usually 8 days with some rain in Decatur in September and the average monthly rainfall is 3.2 inches.

Decatur September sunrise & sunset times

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

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:24 18:27
Monday, 15th September 2025 05:37 18:04
Tuesday, 30th September 2025 05:51 17:39

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