O'Fallon, IL is located in the northern part of Illinois and has a humid continental climate. Summers are hot and humid with temperatures reaching into the mid-90s on some days. Winters are cold and snowy with temperatures dropping to below freezing at night. Spring and fall can bring mild temperatures as well as occasional severe weather events like thunderstorms or tornadoes. Overall, O'Fallon experiences four distinct seasons with moderate amounts of precipitation throughout the year.
O'Fallon, Illinois gets 43 inches of rain, on average, per year. The US average is 38 inches of rain per year.
O'Fallon averages 12 inches of snow per year. The US average is 28 inches of snow per year.
On average, there are 202 sunny days per year in O'Fallon. The US average is 205 sunny days.
O'Fallon gets some kind of precipitation, on average, 96 days per year. Precipitation is rain, snow, sleet, or hail that falls to the ground. In order for precipitation to be counted you have to get at least .01 inches on the ground to measure.
Weather Highlights
Summer High: the July high is around 89 degrees
Winter Low: the January low is 22
Rain: averages 43 inches of rain a year
Snow: averages 12 inches of snow a year