O'Fallon (MO) Weather and Climate: A Comprehensive Guide
The climate in O'Fallon is marked by big temperature swings throughout the year.
Temperatures range from very warm during the warmest months
to cold in the cooler months.
It also has a relatively rain/snowy climate with high levels of precipitation.
Let’s explore the climate details in depth to provide you with a complete overview.
Average maximum day and minimum night temperature
In O'Fallon, temperatures differ significantly between summer and winter months. On average, daytime temperatures range from a very warm 31°C in July to a chilly 5°C in January.
Nighttime temperatures can drop, with average lows reaching -6°C in January. Check out our detailed temperature page for more information.Temperature ranges by month
Precipitation and rainy days
O'Fallon experiences significant rain/snowfall throughout the year, averaging 1086 mm of precipitation annually. The seasons in O'Fallon, bring significant changes in precipitation. The wettest month, June, receives high rainfall, with an average of 119 mm of precipitation. This rainfall is distributed across 12 rainy days. In contrast, the driest month, January, experiences much less snow/rainfall, totaling 44 mm over 7 snowy/rainy days. These distinct seasonal differences provide diverse experiences throughout the year. For more details, please visit our O'Fallon Precipitation page.The mean monthly precipitation over the year, including rain, hail and snow
The average number of days each month with precipitation
Sunshine over the year
In O'Fallon, summer days are longer and more sunny, with daily sunshine hours peaking at 10.4 hours in July. As the darker season arrives, the brightness of the sun becomes less. December sees a soft sun for only 4.3 hours per average day. Visit our detailed sunshine hours page for more information.Monthly hours of sunshine
Daily hours of sunshine
Daily percentage of sunshine
Average humidity
The relative humidity is high throughout the year in O'Fallon.
The city experiences its highest humidity in December, reaching 74%. In April, the humidity drops to its lowest level at 63%. Explore our detailed page on humidity levels for further details.
Relative humidity over the year
clear and no rain clear and no rain overcast and chance of slight rainForecast for O'Fallon (MO)
3 m/s
5 m/s
4 m/s
The best time of year to visit O'Fallon in the United States of America
During the months of April, May and October you are most likely to experience good weather with pleasant average temperatures that fall between 20°C and 26°C.Other facts from our historical weather data:
July has an average maximum temperature of 31°C and is the warmest month of the year.
The coldest month is January with an average maximum temperature of 5°C.
June tops the wettest month list with 119 mm of rainfall.
January is the driest month with 44 mm of precipitation.
July is the sunniest month with an average of 311 hours of sunshine.
No idea where to travel to this year? We have a tool that recommends destinations based on your ideal conditions. Find out where to go with our weather planner.
