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

48°F

9°C

Humidity 61%
Wind Speed S 6 mph
Barometer 29.92 in (1013.4 mb)
Dewpoint 35°F (2°C)
Visibility 10.00 mi
Wind Chill45°F (7°C)
Last update 6 Dec 1:53 pm CST
Extended Forecast for

O'Fallon IL

  • This Afternoon

    This Afternoon: Mostly cloudy, with a high near 43. Southeast wind around 6 mph.

    High: 43 °F

    Mostly Cloudy

  • Tonight

    Tonight: Mostly cloudy, with a low around 33. South wind 5 to 7 mph.

    Low: 33 °F

    Mostly Cloudy

  • Sunday

    Sunday: A slight chance of drizzle before 4pm, then a slight chance of drizzle and snow between 4pm and 5pm, then a slight chance of snow after 5pm. Mostly cloudy, with a high near 39. South wind 5 to 14 mph becoming north in the afternoon. Winds could gust as high as 21 mph. Chance of precipitation is 20%.

    High: 39 °F

    Slight Chance
    Drizzle then
    Slight Chance
    Drizzle/Snow

  • Sunday Night

    Sunday Night: Mostly cloudy, with a low around 20. North wind 7 to 13 mph.

    Low: 20 °F

    Mostly Cloudy

  • Monday

    Monday: Mostly sunny, with a high near 33. North wind around 6 mph becoming calm in the morning.

    High: 33 °F

    Mostly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 24.

    Low: 24 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 50.

    High: 50 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 39.

    Low: 39 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Partly sunny, with a high near 46.

    High: 46 °F

    Partly Sunny

Detailed Forecast

This Afternoon
Mostly cloudy, with a high near 43. Southeast wind around 6 mph.
Tonight
Mostly cloudy, with a low around 33. South wind 5 to 7 mph.
Sunday
A slight chance of drizzle before 4pm, then a slight chance of drizzle and snow between 4pm and 5pm, then a slight chance of snow after 5pm. Mostly cloudy, with a high near 39. South wind 5 to 14 mph becoming north in the afternoon. Winds could gust as high as 21 mph. Chance of precipitation is 20%.
Sunday Night
Mostly cloudy, with a low around 20. North wind 7 to 13 mph.
Monday
Mostly sunny, with a high near 33. North wind around 6 mph becoming calm in the morning.
Monday Night
Partly cloudy, with a low around 24.
Tuesday
Mostly sunny, with a high near 50.
Tuesday Night
Mostly cloudy, with a low around 39.
Wednesday
Partly sunny, with a high near 46.
Wednesday Night
Mostly cloudy, with a low around 26.
Thursday
A slight chance of rain and snow. Mostly cloudy, with a high near 38. Chance of precipitation is 20%.
Thursday Night
Mostly cloudy, with a low around 22.
Friday
Mostly sunny, with a high near 29.
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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:
12:36 pm CST Dec 6, 2025
Forecast Valid:
2pm CST Dec 6, 2025-6pm CST Dec 12, 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