Severe Thunderstorms and Heavy Rain Across the Ohio Valley;

Severe thunderstorms with damaging wind gusts will be possible from the mid-Mississippi Valley into parts of the Ohio Valley and central Appalachians. Heavy rain associated with these storms may lead to considerable flash and urban flooding impacts across portions of the Ohio Valley. Mid-summer heat persists from the Central Plains to the Southeast. Read More >

Current conditions at

St. Louis Downtown Airport (KCPS)

Lat: 38.56°NLon: 90.15°WElev: 410ft.

Fair

91°F

33°C

Humidity 57%
Wind Speed SW 8 mph
Barometer 29.97 in (1014.4 mb)
Dewpoint 74°F (23°C)
Visibility NA
Heat Index100°F (38°C)
Last update 11 Aug 11:53 am CDT
Extended Forecast for

O'Fallon IL

Extreme Heat Warning August 11, 12:45pm until August 12, 08:00pm
Click here for hazard details and duration
Extreme Heat Warning
  •  
    Extreme Heat Warning August 11, 12:45pm until August 12, 08:00pm

    NOW until 8:00pm Wed

    Extreme Heat Warning

  • This Afternoon

    High: 97 °F

    Hot

  • Tonight

    Tonight: Partly cloudy, with a low around 79. South wind around 7 mph.

    Low: 79 °F

    Partly Cloudy

  • Wednesday

    Wednesday: Scattered showers and thunderstorms, mainly between 10am and 11am.  Mostly sunny and hot, with a high near 98. Heat index values as high as 111. Southwest wind 6 to 8 mph.  Chance of precipitation is 30%.

    High: 98 °F

    Scattered
    T-storms

  • Wednesday Night

    Wednesday Night: Isolated showers and thunderstorms.  Partly cloudy, with a low around 77. South wind around 7 mph.  Chance of precipitation is 20%.

    Low: 77 °F

    Isolated
    T-storms

  • Thursday

    Thursday: A 30 percent chance of showers and thunderstorms, mainly after 1pm.  Partly sunny, with a high near 95. South wind 5 to 7 mph becoming east in the afternoon.

    High: 95 °F

    Chance
    T-storms

  • Thursday Night

    Thursday Night: A 40 percent chance of showers and thunderstorms, mainly after 1am.  Mostly cloudy, with a low around 75.

    Low: 75 °F

    Chance
    T-storms

  • Friday

    Friday: Partly sunny, with a high near 92.

    High: 92 °F

    Partly Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 75.

    Low: 75 °F

    Partly Cloudy

Detailed Forecast

This Afternoon
Sunny and hot, with a high near 97. Heat index values as high as 110. Southwest wind around 9 mph.
Tonight
Partly cloudy, with a low around 79. South wind around 7 mph.
Wednesday
Scattered showers and thunderstorms, mainly between 10am and 11am. Mostly sunny and hot, with a high near 98. Heat index values as high as 111. Southwest wind 6 to 8 mph. Chance of precipitation is 30%.
Wednesday Night
Isolated showers and thunderstorms. Partly cloudy, with a low around 77. South wind around 7 mph. Chance of precipitation is 20%.
Thursday
A 30 percent chance of showers and thunderstorms, mainly after 1pm. Partly sunny, with a high near 95. South wind 5 to 7 mph becoming east in the afternoon.
Thursday Night
A 40 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 75.
Friday
Partly sunny, with a high near 92.
Friday Night
Partly cloudy, with a low around 75.
Saturday
Mostly sunny and hot, with a high near 97.
Saturday Night
Mostly clear, with a low around 77.
Sunday
Mostly sunny and hot, with a high near 97.
Sunday Night
A 30 percent chance of showers and thunderstorms. Partly cloudy, with a low around 74.
Monday
A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 88.
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ABOUT THIS FORECAST

 
Point Forecast:
O'Fallon IL
 38.59°N 89.92°W (Elev. 551 ft)
12:21 pm CDT Aug 11, 2026
12pm CDT Aug 11, 2026-6pm CDT Aug 17, 2026
 
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Additional Resources

Radar & Satellite Image

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Hourly Weather Forecast

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