Weather Forecast and Radar for O'Fallon, Illinois

Weather in O'Fallon, IL

O'Fallon, Illinois, United States experiences four distinct seasons throughout the year, each with its own weather patterns. In the winter months, temperatures generally stay below freezing, with the average high temperature ranging from the upper 20s to the mid-30s and lows dropping into the teens. Snowfall is moderate, with an average of 10 inches per month from December through March.

Spring brings milder weather, with temperatures gradually increasing from the mid-40s in March to the mid-60s in May. Rainfall is frequent in the spring, with an average of 3 to 4 inches per month.

Summer in O'Fallon is hot and humid, with temperatures in June and July averaging in the high 70s to the low 80s. There is also a significant amount of rainfall, with an average of 4 to 5 inches per month.

In the fall, temperatures in O'Fallon begin to drop in September, with highs in the mid- to upper-60s and lows in the mid-50s. Rainfall averages 3 to 4 inches per month, and snowfall is rare.

Fast Facts About O'Fallon, IL

As of 2020, the city population is 29487.

Major Cities Nearby O'Fallon, IL

This map shows the current & 7-day weather forecast, weather alerts, and weather radar for O'Fallon, Illinois.