2025 Compare Climate & Weather:
Belleville, IL vs Decatur, IL

Highlights

On average, there are 199 sunny days per year in Decatur. Belleville averages 203 sunny days per year. The US average is 205 sunny days.

Decatur, Illinois gets 39.5 inches of rain, on average, per year. Belleville, Illinois gets 42.3 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

Decatur averages 13 inches of snow per year. Belleville averages 12.7 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

Decatur, Illinois
Summer High: the July high is around 86.9 degrees
Winter Low: the January low is 18.8
Rain: averages 39.5 inches of rain a year
Snow: averages 13 inches of snow a year

Belleville, Illinois
Summer High: the July high is around 89.1 degrees
Winter Low: the January low is 22.2
Rain: averages 42.3 inches of rain a year
Snow: averages 12.7 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for Decatur is 7.2 (10=best), which means it is one of the most pleasant places in Illinois.

The annual BestPlaces Comfort Index for Belleville is 7.2 (10=best), which means it is one of the most pleasant places in Illinois.

Today's Weather - Belleville, IL

52°F

Today's Weather - Decatur, IL

54°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Belleville / Decatur

July is the hottest month for Belleville with an average high temperature of 89.1°, which ranks it as one of the hottest places in Illinois. In Belleville, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Belleville are May, September and June.

July is the hottest month for Decatur with an average high temperature of 86.9°, which ranks it as warmer than most places in Illinois. In Decatur, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Decatur are September, May and June.

January has the coldest nighttime temperatures for Belleville with an average of 22.2°. This is warmer than most places in Illinois.

January has the coldest nighttime temperatures for Decatur with an average of 18.8°. This is warmer than most places in Illinois.

In Belleville, there are 39.3 days annually when the high temperature is over 90°, which is one of the hottest places in Illinois.

In Decatur, there are 24.8 days annually when the high temperature is over 90°, which is hotter than most places in Illinois.

In Belleville, there are 100.0 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Illinois.

In Decatur, there are 112.5 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Illinois.

In Belleville, there are 1.6 days annually when the nighttime low temperature falls below zero°, which is one of the warmest places in Illinois.

In Decatur, there are 4.8 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Illinois.

May is the wettest month in Belleville with 4.8 inches of rain, and the driest month is February with 2.3 inches. The wettest season is Summer with 29% of yearly precipitation and 18% occurs in Spring, which is the driest season. The annual rainfall of 42.3 inches in Belleville means that it is wetter than most places in Illinois.


June is the wettest month in Decatur with 4.5 inches of rain, and the driest month is January with 1.9 inches. The wettest season is Autumn with 31% of yearly precipitation and 16% occurs in Spring, which is the driest season. The annual rainfall of 39.5 inches in Decatur means that it is about average compared to other places in Illinois.

May is the rainiest month in Belleville with 11.1 days of rain, and September is the driest month with only 6.6 rainy days. There are 101.0 rainy days annually in Belleville, which is less rainy than most places in Illinois. The rainiest season is Summer when it rains 30% of the time and the driest is Spring with only a 22% chance of a rainy day.

May is the rainiest month in Decatur with 11.5 days of rain, and September is the driest month with only 6.9 rainy days. There are 104.3 rainy days annually in Decatur, which is less rainy than most places in Illinois. The rainiest season is Summer when it rains 30% of the time and the driest is Spring with only a 23% chance of a rainy day.

An annual snowfall of 12.7 inches in Belleville means that it is less snowy than most places in Illinois.

An annual snowfall of 13.0 inches in Decatur means that it is less snowy than most places in Illinois.

January is the snowiest month in Belleville with 4.1 inches of snow, and 4 months of the year have significant snowfall.

January is the snowiest month in Decatur with 4.2 inches of snow, and 4 months of the year have significant snowfall.