Decatur weather in July 2026

Q: How hot is it in Decatur in July?

Daytime temperatures usually reach 29°C in Decatur in July with moderate heat and humidity, falling to 17°C at night.

Q: How sunny is it in Decatur in July?

There are normally 10 hours of bright sunshine each day in Decatur in July - that's 69% of daylight hours.

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

The average sea temperature around Decatur in July is 19°C.

Q: Does it rain in Decatur in July?

There are usually 10 days with some rain in Decatur in July and the average monthly rainfall is 100mm.

Expect daytime maximum temperatures of 31°C in Decatur, Illinois in July and high heat and humidity based on long-term weather averages. There are 10 hours of sunshine per day on average with typically 107 mm of rainfall in the month.

31
31°C max day temperature
10
10 hours of sunshine per day
9
9 days with some rainfall
18
18°C min night temperature
15
15 hours of daylight per day
H
High heat & humidity
107
107 mm of monthly rainfall
9
9 (Very High) UV index

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The July 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)