2025 Compare Climate & Weather:
O'Fallon, MO vs St. Charles, MO

Highlights

On average, there are 202 sunny days per year in St. Charles. O'Fallon averages 200 sunny days per year. The US average is 205 sunny days.

St. Charles, Missouri gets 42.2 inches of rain, on average, per year. O'Fallon, Missouri gets 42.7 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

St. Charles averages 14.2 inches of snow per year. O'Fallon averages 13.4 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

St. Charles, Missouri
Summer High: the July high is around 88.3 degrees
Winter Low: the January low is 21.3
Rain: averages 42.2 inches of rain a year
Snow: averages 14.2 inches of snow a year

O'Fallon, Missouri
Summer High: the July high is around 88 degrees
Winter Low: the January low is 20.7
Rain: averages 42.7 inches of rain a year
Snow: averages 13.4 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for St. Charles is 7.2 (10=best), which means it is more comfortable than most places in Missouri.

The annual BestPlaces Comfort Index for O'Fallon is 7.2 (10=best), which means it is more comfortable than most places in Missouri.

Today's Weather - O'Fallon, MO

52°F

Today's Weather - St. Charles, MO

53°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: O'Fallon / St. Charles

July is the hottest month for O'Fallon with an average high temperature of 88.0°, which ranks it as about average compared to other places in Missouri. 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 September, May and June.

July is the hottest month for St. Charles with an average high temperature of 88.3°, which ranks it as about average compared to other places in Missouri. In St. Charles, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for St. Charles are September, May and June.

January has the coldest nighttime temperatures for O'Fallon with an average of 20.7°. This is about average compared to other places in Missouri.

January has the coldest nighttime temperatures for St. Charles with an average of 21.3°. This is warmer than most places in Missouri.

In O'Fallon, there are 32.2 days annually when the high temperature is over 90°, which is about average compared to other places in Missouri.

In St. Charles, there are 33.5 days annually when the high temperature is over 90°, which is about average compared to other places in Missouri.

In O'Fallon, there are 104.1 days annually when the nighttime low temperature falls below freezing, which is about average compared to other places in Missouri.

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

In O'Fallon, there are 3.1 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in Missouri.

In St. Charles, there are 2.7 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in Missouri.

May is the wettest month in O'Fallon with 4.9 inches of rain, and the driest month is January with 2.4 inches. The wettest season is Summer with 29% of yearly precipitation and 19% occurs in Spring, which is the driest season. The annual rainfall of 42.7 inches in O'Fallon means that it is drier than most places in Missouri.


May is the wettest month in St. Charles with 4.9 inches of rain, and the driest month is January with 2.4 inches. The wettest season is Summer with 29% of yearly precipitation and 19% occurs in Spring, which is the driest season. The annual rainfall of 42.2 inches in St. Charles means that it is drier than most places in Missouri.

May is the rainiest month in O'Fallon with 11.6 days of rain, and January is the driest month with only 7.2 rainy days. There are 106.5 rainy days annually in O'Fallon, which is one of the rainiest places in Missouri. 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 St. Charles with 11.5 days of rain, and September is the driest month with only 7.3 rainy days. There are 105.9 rainy days annually in St. Charles, which is one of the rainiest places in Missouri. 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.

An annual snowfall of 13.4 inches in O'Fallon means that it is about average compared to other places in Missouri.

An annual snowfall of 14.2 inches in St. Charles means that it is snowier than most places in Missouri.

February is the snowiest month in O'Fallon with 4.5 inches of snow, and 5 months of the year have significant snowfall.

January is the snowiest month in St. Charles with 4.4 inches of snow, and 5 months of the year have significant snowfall.