Live Weather & Forecast
Weather in O'Fallon
Illinois, United States · Real-time conditions & 3-day outlook
25°C
Feels like 26°C
77°F / Feels 78°F
Partly cloudy
O'Fallon, Illinois
🌞 Daytime
Updated: 2026-04-12 15:45
Humidity
42%
Wind
29.5 km/h SSW
Wind Gust
44.3 km/h
Pressure
1015 mb
Visibility
16 km
UV Index
5
(Moderate)
Precipitation
0 mm
Cloud Cover
75%
Dew Point
15.2°C
Wind Degree
195°
Air Quality Index
US EPA: Good
UK DEFRA: Low (1)
CO
155.9 μg/m³
NO₂
4.5 μg/m³
O₃
111 μg/m³
SO₂
2.6 μg/m³
PM 2.5
5.8 μg/m³
PM 10
6.2 μg/m³
Weather Alerts 1
Met
· Moderate · Expected
Special Weather Statement issued April 12 at 12:21AM CDT by NWS Paducah KY
Elevated conditions for wildfires are expected this afternoon, mainly between 12 PM and 7 PM CDT. Relative humidity values will fall to 25 to 35% this afternoon, and winds will be breezy from the south, sustained at 10 to 15 mph with gusts of 25 to 30 mph forecast. Vegetation is dry due to ongoing moderate to severe drought conditions over much of the region. Outdoor burning and activities that i...
Today's Hourly Forecast
24-hour breakdown for O'Fallon, Illinois
12 AM
16°
Clear
1 AM
16°
Clear
2 AM
16°
Clear
3 AM
15°
Clear
4 AM
15°
Clear
5 AM
15°
Clear
6 AM
14°
Clear
7 AM
15°
Sunny
8 AM
17°
Sunny
9 AM
19°
Sunny
10 AM
23°
Sunny
11 AM
25°
Sunny
12 PM
27°
Sunny
1 PM
27°
Sunny
2 PM
28°
Sunny
3 PM
25°
Partly cloudy
4 PM
27°
Sunny
5 PM
26°
Overcast
6 PM
24°
Overcast
7 PM
23°
Overcast
8 PM
22°
Overcast
9 PM
22°
Cloudy
10 PM
21°
Overcast
11 PM
20°
Partly Cloudy
3-Day Forecast
Daily overview for O'Fallon, Illinois
Today
Sunny
30°
/
14°
🌧️ 0% chance of rain
💧 Avg. humidity: 67%
💨 Max wind: 32 km/h
🌧️ Total precip: 0 mm
☀️ UV Index: 1.7
🌅 Sunrise: 06:27 AM
🌇 Sunset: 07:34 PM
🌙 Waning Crescent
🌑 Moon: 33% lit
Mon, Apr 13
Cloudy
26°
/
17°
🌧️ 0% chance of rain
💧 Avg. humidity: 74%
💨 Max wind: 30.2 km/h
🌧️ Total precip: 0 mm
☀️ UV Index: 2
🌅 Sunrise: 06:26 AM
🌇 Sunset: 07:35 PM
🌙 Waning Crescent
🌑 Moon: 23% lit
Tue, Apr 14
Overcast
25°
/
19°
🌧️ 0% chance of rain
💧 Avg. humidity: 79%
💨 Max wind: 33.1 km/h
🌧️ Total precip: 0 mm
☀️ UV Index: 2
🌅 Sunrise: 06:24 AM
🌇 Sunset: 07:36 PM
🌙 Waning Crescent
🌑 Moon: 15% lit
Best Time to Visit O'Fallon
Plan your trip to O'Fallon, United States around the most favorable weather conditions.
Peak Season
June – September
Warm, dry summers — ideal for outdoor activities.
Shoulder Season
April – May, October
Fewer crowds, moderate prices, mild weather.
Off Season
November – March
Cooler temperatures; some regions may experience rain or snow.
Frequently Asked Questions
What is the current weather in O'Fallon?
Current conditions in O'Fallon: Partly cloudy, temperature 25°C, humidity 42%.
What is the best time to visit O'Fallon?
The best time to visit O'Fallon is typically June – September. Warm, dry summers — ideal for outdoor activities.
What is the climate like in O'Fallon?
O'Fallon is located at approximately 38.6° latitude. It has a temperate climate with warm summers and cold winters.
Does it rain a lot in O'Fallon?
The wettest period in O'Fallon is typically during November – March. Cooler temperatures; some regions may experience rain or snow.
What should I pack for a trip to O'Fallon?
For visits to O'Fallon during June – September: light clothing and sun protection. For November – March: layers and a waterproof jacket are recommended.
What country is O'Fallon in?
O'Fallon is located in United States, in the state of Illinois.
What are the public holidays in O'Fallon in 2026?
View the 2026 public holidays for O'Fallon on our Holidays page.
What are the GPS coordinates used for the weather forecast in O'Fallon?
The weather forecast for O'Fallon uses coordinates 38.5923, -89.9112.