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.

Overcast

26°F

-3°C

Humidity 78%
Wind Speed Calm
Barometer 30.10 in (1019.8 mb)
Dewpoint 20°F (-7°C)
Visibility 10.00 mi
Last update 2 Dec 4:53 pm CST
Extended Forecast for

O'Fallon IL

  • Tonight

    Tonight: Partly cloudy, with a low around 19. Calm wind becoming south around 6 mph in the evening.

    Low: 19 °F

    Partly Cloudy

  • Wednesday

    Wednesday: Increasing clouds, with a high near 40. South wind around 7 mph becoming northwest in the afternoon.

    High: 40 °F

    Increasing
    Clouds

  • Wednesday Night

    Wednesday Night: A 20 percent chance of snow after midnight. Mostly cloudy, with a low around 16. North wind 6 to 11 mph.

    Low: 16 °F

    Mostly Cloudy
    then Slight
    Chance Snow

  • Thursday

    Thursday: Mostly sunny, with a high near 24. North wind 5 to 10 mph becoming light in the afternoon.

    High: 24 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 13. Calm wind.

    Low: 13 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 38.

    High: 38 °F

    Mostly Sunny

  • Friday Night

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

    Low: 23 °F

    Mostly Cloudy

  • Saturday

    Saturday: Partly sunny, with a high near 38.

    High: 38 °F

    Partly Sunny

  • Saturday Night

    Saturday Night: Mostly cloudy, with a low around 25.

    Low: 25 °F

    Mostly Cloudy

Detailed Forecast

Tonight
Partly cloudy, with a low around 19. Calm wind becoming south around 6 mph in the evening.
Wednesday
Increasing clouds, with a high near 40. South wind around 7 mph becoming northwest in the afternoon.
Wednesday Night
A 20 percent chance of snow after midnight. Mostly cloudy, with a low around 16. North wind 6 to 11 mph.
Thursday
Mostly sunny, with a high near 24. North wind 5 to 10 mph becoming light in the afternoon.
Thursday Night
Partly cloudy, with a low around 13. Calm wind.
Friday
Mostly sunny, with a high near 38.
Friday Night
Mostly cloudy, with a low around 23.
Saturday
Partly sunny, with a high near 38.
Saturday Night
Mostly cloudy, with a low around 25.
Sunday
A 20 percent chance of rain after noon. Mostly cloudy, with a high near 35.
Sunday Night
A slight chance of rain and snow. Mostly cloudy, with a low around 20. Chance of precipitation is 20%.
Monday
Partly sunny, with a high near 34.
Monday Night
A 20 percent chance of snow. Mostly cloudy, with a low around 26.
Tuesday
Partly sunny, with a high near 41.
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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:
4:51 pm CST Dec 2, 2025
Forecast Valid:
5pm CST Dec 2, 2025-6pm CST Dec 9, 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