National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce
Current conditions at

St. Louis Downtown Airport (KCPS)

Lat: 38.56°NLon: 90.15°WElev: 410ft.

Fair

23°F

-5°C

Humidity 63%
Wind Speed NE 6 mph
Barometer 30.32 in (1027.1 mb)
Dewpoint 12°F (-11°C)
Visibility 10.00 mi
Wind Chill16°F (-9°C)
Last update 4 Dec 4:53 pm CST
Extended Forecast for

O'Fallon IL

  • Tonight

    Tonight: Mostly clear, with a low around 9. Light and variable wind.

    Low: 9 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 37. Calm wind becoming south 5 to 7 mph in the morning.

    High: 37 °F

    Sunny

  • Friday Night

    Friday Night: Increasing clouds, with a low around 27. South wind 5 to 7 mph becoming west after midnight.

    Low: 27 °F

    Increasing
    Clouds

  • Saturday

    Saturday: Partly sunny, with a high near 37. Light and variable wind becoming north around 5 mph in the afternoon.

    High: 37 °F

    Partly Sunny

  • Saturday Night

    Saturday Night: A 20 percent chance of snow after midnight. Mostly cloudy, with a low around 29. East wind 3 to 6 mph.

    Low: 29 °F

    Mostly Cloudy
    then Slight
    Chance Snow

  • Sunday

    Sunday: A chance of rain and snow, mainly before noon. Mostly cloudy, with a high near 37. Chance of precipitation is 30%.

    High: 37 °F

    Chance
    Rain/Snow

  • Sunday Night

    Sunday Night: Mostly cloudy, with a low around 17.

    Low: 17 °F

    Mostly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 32.

    High: 32 °F

    Mostly Sunny

  • Monday Night

    Monday Night: Mostly cloudy, with a low around 23.

    Low: 23 °F

    Mostly Cloudy

Detailed Forecast

Tonight
Mostly clear, with a low around 9. Light and variable wind.
Friday
Sunny, with a high near 37. Calm wind becoming south 5 to 7 mph in the morning.
Friday Night
Increasing clouds, with a low around 27. South wind 5 to 7 mph becoming west after midnight.
Saturday
Partly sunny, with a high near 37. Light and variable wind becoming north around 5 mph in the afternoon.
Saturday Night
A 20 percent chance of snow after midnight. Mostly cloudy, with a low around 29. East wind 3 to 6 mph.
Sunday
A chance of rain and snow, mainly before noon. Mostly cloudy, with a high near 37. Chance of precipitation is 30%.
Sunday Night
Mostly cloudy, with a low around 17.
Monday
Mostly sunny, with a high near 32.
Monday Night
Mostly cloudy, with a low around 23.
Tuesday
Mostly sunny, with a high near 45.
Tuesday Night
Mostly cloudy, with a low around 32.
Wednesday
A 30 percent chance of rain. Mostly cloudy, with a high near 47.
Wednesday Night
Mostly cloudy, with a low around 23.
Thursday
Partly sunny, with a high near 34.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
O'Fallon IL
 38.59°N 89.92°W (Elev. 551 ft)
Last Update:
3:16 pm CST Dec 4, 2025
Forecast Valid:
5pm CST Dec 4, 2025-6pm CST Dec 11, 2025
 
Forecast Discussion
 
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Additional Resources

Radar & Satellite Image

Link to Local Radar Data Link to Satellite Data

Hourly Weather Forecast

National Digital Forecast Database

National Digital Forecast Database Maximum Temperature Forecast

High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation