O'Fallon, MO Weather
O'Fallon, MO climate is warm during summer when temperatures tend to be in the 70's and very cold during winter when temperatures tend to be in the 30's.
The warmest month of the year is July with an average maximum temperature of 9.99 degrees Fahrenheit, while the coldest month of the year is January with an average minimum temperature of 9.99 degrees Fahrenheit.
Temperature variations between night and day tend to be moderate during summer with a difference that can reach 23 degrees Fahrenheit, and fairly limited during winter with an average difference of 19 degrees Fahrenheit.
The annual average precipitation at O'Fallon is 9.99 Inches. Rainfall in is fairly evenly distributed throughout the year. The wettest month of the year is July with an average rainfall of 4.18 Inches.