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.

Overcast

79°F

26°C

Humidity 88%
Wind Speed SW 6 mph
Barometer 29.90 in (1012.2 mb)
Dewpoint 75°F (24°C)
Visibility 10.00 mi
Heat Index83°F (28°C)
Last update 27 Jun 9:53 am CDT
Extended Forecast for

O'Fallon IL

Extreme Heat Watch June 28, 12:00pm until July 3, 12:00am
Click here for hazard details and duration
Extreme Heat Watch

  • Today

    Today: A 50 percent chance of showers and thunderstorms, mainly before 5pm. Partly sunny, with a high near 85. Southwest wind 3 to 5 mph.

    High: 85 °F

    Chance
    T-storms

  • Tonight

    Tonight: A 40 percent chance of showers and thunderstorms, mainly between 8pm and 5am. Increasing clouds, with a low around 72. Calm wind becoming south around 5 mph after midnight.

    Low: 72 °F

    Chance
    T-storms

  • Sunday

    Sunday: Partly sunny, then gradually becoming sunny, with a high near 93. Heat index values as high as 110. South wind 6 to 10 mph.

    High: 93 °F

    Becoming
    Sunny

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 75. South wind 5 to 10 mph.

    Low: 75 °F

    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 95. South wind 6 to 11 mph.

    High: 95 °F

    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 75.

    Low: 75 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 96.

    High: 96 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Clear, with a low around 76.

    Low: 76 °F

    Clear

  • Wednesday

    Wednesday: Sunny, with a high near 96.

    High: 96 °F

    Sunny

Detailed Forecast

Today
A 50 percent chance of showers and thunderstorms, mainly before 5pm. Partly sunny, with a high near 85. Southwest wind 3 to 5 mph.
Tonight
A 40 percent chance of showers and thunderstorms, mainly between 8pm and 5am. Increasing clouds, with a low around 72. Calm wind becoming south around 5 mph after midnight.
Sunday
Partly sunny, then gradually becoming sunny, with a high near 93. Heat index values as high as 110. South wind 6 to 10 mph.
Sunday Night
Mostly clear, with a low around 75. South wind 5 to 10 mph.
Monday
Sunny, with a high near 95. South wind 6 to 11 mph.
Monday Night
Mostly clear, with a low around 75.
Tuesday
Sunny, with a high near 96.
Tuesday Night
Clear, with a low around 76.
Wednesday
Sunny, with a high near 96.
Wednesday Night
Mostly clear, with a low around 77.
Thursday
Sunny, with a high near 94.
Thursday Night
Mostly clear, with a low around 76.
Friday
A 20 percent chance of showers and thunderstorms. Sunny, with a high near 94.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
O'Fallon IL
 38.59°N 89.89°W (Elev. 541 ft)
Last Update:
9:26 am CDT Jun 27, 2026
Forecast Valid:
10am CDT Jun 27, 2026-6pm CDT Jul 3, 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