O'Fallon, MO has a humid continental climate, with hot summers and cold winters. In the summer months, temperatures often reach into the mid-90s and can be quite humid due to the moisture in the nearby Mississippi River. In the winter months, temperatures typically drop to near freezing and can occasionally dip below zero. Precipitation is fairly evenly distributed throughout the year, though snowfall tends to occur more frequently in December through February.
O'Fallon, Missouri gets 43 inches of rain, on average, per year. The US average is 38 inches of rain per year.
O'Fallon averages 13 inches of snow per year. The US average is 28 inches of snow per year.
On average, there are 200 sunny days per year in O'Fallon. The US average is 205 sunny days.
O'Fallon gets some kind of precipitation, on average, 107 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 88 degrees
Winter Low: the January low is 21
Rain: averages 43 inches of rain a year
Snow: averages 13 inches of snow a year