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.

Partly Cloudy

81°F

27°C

Humidity 69%
Wind Speed W 8 mph
Barometer 29.91 in (1012.5 mb)
Dewpoint 70°F (21°C)
Visibility 10.00 mi
Heat Index84°F (29°C)
Last update 15 Oct 4:53 pm CDT
Extended Forecast for

O'Fallon IL

  • This Afternoon

    This Afternoon: A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 81. Southwest wind around 11 mph.

    High: 81 °F

    Chance
    T-storms

  • Tonight

    Tonight: Showers and thunderstorms likely before 1am, then a slight chance of showers between 1am and 4am. Increasing clouds, with a low around 48. Southwest wind 10 to 18 mph becoming northwest after midnight. Winds could gust as high as 26 mph. Chance of precipitation is 60%.

    Low: 48 °F

    Showers
    Likely

  • Friday

    Friday: A 20 percent chance of showers after 4pm. Cloudy through mid morning, then clearing, with a high near 56. Breezy, with a northwest wind 17 to 21 mph, with gusts as high as 29 mph.

    High: 56 °F

    Breezy.
    Clearing then
    Slight Chance
    Showers

  • Friday Night

    Friday Night: Mostly cloudy, then gradually becoming mostly clear, with a low around 39. Northwest wind 9 to 17 mph, with gusts as high as 25 mph.

    Low: 39 °F

    Decreasing
    Clouds

  • Saturday

    Saturday: Sunny, with a high near 59. North wind 5 to 7 mph becoming calm in the afternoon.

    High: 59 °F

    Sunny

  • Saturday Night

    Saturday Night: Clear, with a low around 36.

    Low: 36 °F

    Clear

  • Sunday

    Sunday: Sunny, with a high near 67.

    High: 67 °F

    Sunny

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 40.

    Low: 40 °F

    Mostly Clear

  • Monday

    Monday: Mostly sunny, with a high near 71.

    High: 71 °F

    Mostly Sunny

Detailed Forecast

This Afternoon
A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 81. Southwest wind around 11 mph.
Tonight
Showers and thunderstorms likely before 1am, then a slight chance of showers between 1am and 4am. Increasing clouds, with a low around 48. Southwest wind 10 to 18 mph becoming northwest after midnight. Winds could gust as high as 26 mph. Chance of precipitation is 60%.
Friday
A 20 percent chance of showers after 4pm. Cloudy through mid morning, then clearing, with a high near 56. Breezy, with a northwest wind 17 to 21 mph, with gusts as high as 29 mph.
Friday Night
Mostly cloudy, then gradually becoming mostly clear, with a low around 39. Northwest wind 9 to 17 mph, with gusts as high as 25 mph.
Saturday
Sunny, with a high near 59. North wind 5 to 7 mph becoming calm in the afternoon.
Saturday Night
Clear, with a low around 36.
Sunday
Sunny, with a high near 67.
Sunday Night
Mostly clear, with a low around 40.
Monday
Mostly sunny, with a high near 71.
Monday Night
Partly cloudy, with a low around 45.
Tuesday
Mostly sunny, with a high near 76.
Tuesday Night
Mostly clear, with a low around 48.
Wednesday
Sunny, with a high near 79.
Wednesday Night
Mostly clear, with a low around 50.
Thursday
Sunny, with a high near 81.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
O'Fallon IL
 38.59°N 89.95°W (Elev. 545 ft)
Last Update:
2:26 pm CDT Oct 15, 2026
Forecast Valid:
4pm CDT Oct 15, 2026-6pm CDT Oct 22, 2026
 
Forecast Discussion
 
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Additional Resources

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High Temperature

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Chance of Precipitation