Decatur Weather in September

What's the weather like in Decatur (Illinois) in September 2025?

The climate in Decatur during September can be summarized as warm and a little damp.

September is in the fall / autumn in Decatur and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 26°C (79°F), whilst at night 13°C (55°F) is normal.

Decatur weather averages (imperial / metric)
Daytime temperature 26.3°C 79.3°F
Nightly temperature 12.7°C 54.9°F
Average temperature 19.5°C 67.1°F
Daily sunshine 8.7 hrs
Avg rainfall 81 mm 3.2 ins
Rainy days 9 days
Sea temperature 20.8°C 69.4°F
Humidity 72%
Windspeed 14kph 9 mph

On average September is the 6th wettest month of the year in Decatur with around 81mm 3.2 inches of rain making it a a little damp time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 8.7 hours of sunshine per day.

September temperatures in Decatur

Decatur average temperature in September

September rainfall

Decatur average rain in September

September hourly sunshine

Decatur average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Decatur in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Decatur weather stats

Decatur weather statistics
Hottest month: July 30.5°C 86.9°F
Driest month: February 48mm 1.9ins
Sunniest month: July 10.9hrs
Coldest month: January 0.4°C 32.7°F
Wettest month: July 107mm 4.2ins
Map showing location of Decatur (39.84031, -88.9548) Decatur map pin © Google

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