Decatur weather in October 2026

Q: How warm is it in Decatur in October?

Daytime temperatures usually reach 17°C in Decatur in October, falling to 6°C at night.

Q: How sunny is it in Decatur in October?

There are normally 6 hours of bright sunshine each day in Decatur in October - that's 56% of daylight hours.

Q: How warm is the sea around Decatur in October?

The average sea temperature around Decatur in October is 14°C.

Q: Does it rain in Decatur in October?

There are usually 9 days with some rain in Decatur in October and the average monthly rainfall is 68mm.

Expect daytime maximum temperatures of 20°C in Decatur, Illinois in October based on long-term weather averages. There are 7 hours of sunshine per day on average with typically 70 mm of rainfall in the month.

20
20°C max day temperature
7
7 hours of sunshine per day
8
8 days with some rainfall
6
6°C min night temperature
11
11 hours of daylight per day
0
No heat & humidity
70
70 mm of monthly rainfall
4
4 (Moderate) UV index

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The October 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 / mm) | Imperial (°F / inches)