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

Hazardous Weather Conditions

Current conditions at

St. Louis Downtown Airport (KCPS)

Lat: 38.56°NLon: 90.15°WElev: 410ft.

Mostly Cloudy

74°F

23°C

Humidity 88%
Wind Speed Calm
Barometer 30.03 in (1016.5 mb)
Dewpoint 70°F (21°C)
Visibility 10.00 mi
Last update 25 Jul 9:53 am CDT
Extended Forecast for

O'Fallon IL

Heat Advisory July 26, 11:00am until July 27, 09:00pm
Click here for hazard details and duration
Heat Advisory

  • Today

    Today: Scattered showers and thunderstorms before noon, then isolated showers between noon and 1pm. Partly sunny, with a high near 87. Calm wind becoming southwest around 5 mph in the afternoon. Chance of precipitation is 30%.

    High: 87 °F

    Scattered
    Showers

  • Tonight

    Tonight: Partly cloudy, with a low around 73. Light southeast wind.

    Low: 73 °F

    Partly Cloudy

  • Sunday

    Sunday: Mostly sunny, with a high near 93. Heat index values as high as 107. Light and variable wind.

    High: 93 °F

    Mostly Sunny

  • Sunday Night

    Sunday Night: Partly cloudy, with a low around 75. Calm wind becoming southwest around 5 mph after midnight.

    Low: 75 °F

    Partly Cloudy

  • Monday

    Monday: Sunny and hot, with a high near 98. Southwest wind 5 to 11 mph.

    High: 98 °F

    Hot

  • Monday Night

    Monday Night: Mostly clear, with a low around 78.

    Low: 78 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 94.

    High: 94 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 71.

    Low: 71 °F

    Partly Cloudy

  • Wednesday

    Wednesday: Sunny, with a high near 91.

    High: 91 °F

    Sunny

Detailed Forecast

Today
Scattered showers and thunderstorms before noon, then isolated showers between noon and 1pm. Partly sunny, with a high near 87. Calm wind becoming southwest around 5 mph in the afternoon. Chance of precipitation is 30%.
Tonight
Partly cloudy, with a low around 73. Light southeast wind.
Sunday
Mostly sunny, with a high near 93. Heat index values as high as 107. Light and variable wind.
Sunday Night
Partly cloudy, with a low around 75. Calm wind becoming southwest around 5 mph after midnight.
Monday
Sunny and hot, with a high near 98. Southwest wind 5 to 11 mph.
Monday Night
Mostly clear, with a low around 78.
Tuesday
Sunny, with a high near 94.
Tuesday Night
Partly cloudy, with a low around 71.
Wednesday
Sunny, with a high near 91.
Wednesday Night
Mostly clear, with a low around 71.
Thursday
Mostly sunny, with a high near 91.
Thursday Night
A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 72.
Friday
A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 90.
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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:
10:26 am CDT Jul 25, 2026
Forecast Valid:
10am CDT Jul 25, 2026-6pm CDT Jul 31, 2026
 
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