Thunderstorms and Heavy Rainfall in the Plains; Hazardous Heat in the South and Southeast

Severe thunderstorms will be possible across the northern/central Plains through Tuesday afternoon and from the central Plains to the Mid-Mississippi Valley Tuesday evening through Wednesday morning. Storms may produce large hail and damaging wind gusts, and heavy rainfall may lead to scattered instances of flash flooding. Meanwhile, hazardous heat persists across the South and Southeast. Read More >

Current conditions at

St. Charles, St. Charles County Smartt Airport (KSET)

Lat: 38.93°NLon: 90.43°WElev: 436ft.

Fair

68°F

20°C

Humidity 93%
Wind Speed Calm
Barometer 30.05 in (1017.3 mb)
Dewpoint 66°F (19°C)
Visibility 10.00 mi
Last update 17 Aug 10:54 pm CDT
Extended Forecast for

Grafton IL

  • Tonight

    Tonight: Mostly cloudy, then gradually becoming clear, with a low around 64. Calm wind.

    Low: 64 °F

    Decreasing
    Clouds

  • Tuesday

    Tuesday: Mostly sunny, with a high near 86. Calm wind becoming southwest around 6 mph in the morning.

    High: 86 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Showers and thunderstorms likely, mainly after 4am. Some of the storms could produce heavy rainfall.  Increasing clouds, with a low around 70. Southeast wind around 5 mph becoming light and variable.  Chance of precipitation is 70%.

    Low: 70 °F

    Partly Cloudy
    then Heavy
    Rain

  • Wednesday

    Wednesday: Showers and thunderstorms likely, mainly before 9am. Some of the storms could produce heavy rainfall.  Mostly cloudy, with a high near 82. South wind 5 to 7 mph becoming north in the afternoon.  Chance of precipitation is 60%.

    High: 82 °F

    Heavy Rain

  • Wednesday Night

    Wednesday Night: A 40 percent chance of showers and thunderstorms.  Mostly cloudy, with a low around 67. Northeast wind 3 to 7 mph.

    Low: 67 °F

    Chance
    T-storms

  • Thursday

    Thursday: A 20 percent chance of showers and thunderstorms before 1pm.  Mostly sunny, with a high near 82.

    High: 82 °F

    Slight Chance
    T-storms

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 64.

    Low: 64 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 84.

    High: 84 °F

    Sunny

  • Friday Night

    Friday Night: A 20 percent chance of showers after 1am.  Mostly clear, with a low around 66.

    Low: 66 °F

    Mostly Clear
    then Slight
    Chance
    Showers

Detailed Forecast

Tonight
Mostly cloudy, then gradually becoming clear, with a low around 64. Calm wind.
Tuesday
Mostly sunny, with a high near 86. Calm wind becoming southwest around 6 mph in the morning.
Tuesday Night
Showers and thunderstorms likely, mainly after 4am. Some of the storms could produce heavy rainfall. Increasing clouds, with a low around 70. Southeast wind around 5 mph becoming light and variable. Chance of precipitation is 70%.
Wednesday
Showers and thunderstorms likely, mainly before 9am. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 82. South wind 5 to 7 mph becoming north in the afternoon. Chance of precipitation is 60%.
Wednesday Night
A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 67. Northeast wind 3 to 7 mph.
Thursday
A 20 percent chance of showers and thunderstorms before 1pm. Mostly sunny, with a high near 82.
Thursday Night
Mostly clear, with a low around 64.
Friday
Sunny, with a high near 84.
Friday Night
A 20 percent chance of showers after 1am. Mostly clear, with a low around 66.
Saturday
A 20 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 84.
Saturday Night
Mostly clear, with a low around 64.
Sunday
Mostly sunny, with a high near 82.
Sunday Night
Partly cloudy, with a low around 63.
Monday
Partly sunny, with a high near 84.
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ABOUT THIS FORECAST

 
Point Forecast:
Grafton IL
 38.98°N 90.42°W (Elev. 673 ft)
10:31 pm CDT Aug 17, 2026
11pm CDT Aug 17, 2026-6pm CDT Aug 24, 2026
 
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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