2025 Compare Climate & Weather:
O'Fallon, IL vs Lafayette, IN

Highlights

On average, there are 187 sunny days per year in Lafayette. O'Fallon averages 202 sunny days per year. The US average is 205 sunny days.

Lafayette, Indiana gets 37.9 inches of rain, on average, per year. O'Fallon, Illinois gets 43.1 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

Lafayette averages 19.4 inches of snow per year. O'Fallon averages 11.6 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

Lafayette, Indiana
Summer High: the July high is around 86.5 degrees
Winter Low: the January low is 17
Rain: averages 37.9 inches of rain a year
Snow: averages 19.4 inches of snow a year

O'Fallon, Illinois
Summer High: the July high is around 89.2 degrees
Winter Low: the January low is 22
Rain: averages 43.1 inches of rain a year
Snow: averages 11.6 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for Lafayette is 7.0 (10=best), which means it is about average compared to other places in Indiana.

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

Today's Weather - O'Fallon, IL

59°F

Today's Weather - Lafayette, IN

58°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: O'Fallon / Lafayette

July is the hottest month for O'Fallon with an average high temperature of 89.2°, which ranks it as one of the hottest places in Illinois. In O'Fallon, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for O'Fallon are May, September and October.

July is the hottest month for Lafayette with an average high temperature of 86.5°, which ranks it as warmer than most places in Indiana. In Lafayette, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Lafayette are September, May and June.

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.

January has the coldest nighttime temperatures for Lafayette with an average of 17.0°. This is colder than most places in Indiana.

In O'Fallon, there are 39.8 days annually when the high temperature is over 90°, which is one of the hottest places in Illinois.

In Lafayette, there are 26.7 days annually when the high temperature is over 90°, which is hotter than most places in Indiana.

In O'Fallon, there are 101.4 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Illinois.

In Lafayette, there are 122.9 days annually when the nighttime low temperature falls below freezing, which is about average compared to other places in Indiana.

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

In Lafayette, there are 6.7 days annually when the nighttime low temperature falls below zero°, which is colder than most places in Indiana.

May is the wettest month in O'Fallon with 4.9 inches of rain, and the driest month is February with 2.4 inches. The wettest season is Summer with 28% of yearly precipitation and 18% occurs in Spring, which is the driest season. The annual rainfall of 43.1 inches in O'Fallon means that it is wetter than most places in Illinois.


May is the wettest month in Lafayette with 4.5 inches of rain, and the driest month is February with 1.9 inches. The wettest season is Autumn with 32% of yearly precipitation and 17% occurs in Spring, which is the driest season. The annual rainfall of 37.9 inches in Lafayette means that it is one of the driest places in Indiana.

May is the rainiest month in O'Fallon with 10.9 days of rain, and February is the driest month with only 6.6 rainy days. There are 96.4 rainy days annually in O'Fallon, which is one of the least rainy 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 Lafayette with 11.9 days of rain, and September is the driest month with only 8.1 rainy days. There are 119.6 rainy days annually in Lafayette, which is rainier than most places in Indiana. The rainiest season is Summer when it rains 28% of the time and the driest is Winter with only a 23% chance of a rainy day.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.

An annual snowfall of 19.4 inches in Lafayette means that it is about average compared to other places in Indiana.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.

January is the snowiest month in Lafayette with 5.9 inches of snow, and 4 months of the year have significant snowfall.