Yosemite National Park is definitely worth a visit
Vast forests, blue lakes, towering sequoias, and majestic waterfalls hint at the beauty of Yosemite National Park—a true natural masterpiece.
O'Fallon (MO) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit O'Fallon.
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Climate overview of O'Fallon
The climate in O'Fallon, Missouri, United States of America, is marked by large temperature swings across the seasons, ranging from 31°C (88°F) in July to 5°C (41°F) in January.
The city has a wet climate, receiving around 1086 mm (43 in) of rain/snowfall per year. Despite the high annual total, it has very warm summers and cold winters. June is the wettest month. Sunshine peaks in July, when the city sees around 10.4 hours of sunshine per day.
O'Fallon Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in O'Fallon - and find the best time to visit.
Monthly Temperature in O'Fallon
In O'Fallon, temperatures differ significantly between summer and winter months. On average, daytime temperatures range from a very warm 31°C (88°F) in July to a chilly 5°C (41°F) in January.
Nighttime temperatures range from 20°C (68°F) in July to -6°C (21°F) in January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in O'Fallon
O'Fallon experiences significant rain/snowfall throughout the year, averaging 1086 mm (43 in) 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 (4.7 in) of precipitation. This rainfall is distributed across 12 rainy days.
In contrast, the driest month, January, experiences much less snow/rainfall, totaling 44 mm (1.7 in) 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 Hours in O'Fallon
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
Data from: St. Louis, the United States of America (48 KM, 29 Miles).
Daily hours of sunshine
Data from: St. Louis, the United States of America (48 KM, 29 Miles).
Daily percentage of sunshine
Data from: St. Louis, the United States of America (48 KM, 29 Miles).
Humidity in O'Fallon by Month
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%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Data from: St. Louis, the United States of America (48 KM, 29 Miles).
Best Time to Visit O'Fallon
The most comfortable overall weather for exploring O'Fallon is usually found in October. Conditions are generally least comfortable in January, February and December.
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
Jan
cold
Feb
cold
Mar
good
Apr
very good
May
very good
Jun
mixed
Jul
mixed
Aug
good
Sep
very good
Oct
excellent
Nov
mixed
Dec
cold
- Best overall: October
- Warmest weather: June, July and August
- Most sunshine: July
- Seasonal pattern: Very warm summers and cold winters
- Coldest conditions: January, with freezing nights around -6°C (21°F).
Frequently asked questions about the climate in O'Fallon
What is the best time to visit O'Fallon?
October typically offers the most optimal weather in O'Fallon. In contrast, January, February and December tend to have less optimal conditions. O'Fallon has very warm summers and cold winters.
What temperatures can I expect in O'Fallon?
Daytime highs range from 5°C (41°F) in January to 31°C (88°F) in July. Nighttime lows range from -6°C (21°F) to 20°C (68°F). Temperatures vary considerably through the year.
How much rain does O'Fallon get?
Annual rainfall is around 1086 mm (43 in). June is the wettest month with 119 mm (4.7 in), while January is the driest with 44 mm (1.7 in).
How sunny is O'Fallon?
O'Fallon receives around 2,594 hours of sunshine per year. July is the sunniest month with 311 hours, while December is the cloudiest with just 128 hours. Overall, O'Fallon enjoys abundant sunshine.
O'Fallon 3-Day Forecast
O'Fallon on the map
O'Fallon is highlighted - select any city to see its climate.
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Where to go in October - average daytime high across popular destinations.
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