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

72°F

22°C

Humidity 84%
Wind Speed NW 5 mph
Barometer 30.02 in (1016.3 mb)
Dewpoint 67°F (19°C)
Visibility 10.00 mi
Last update 17 Aug 8:54 pm CDT
Extended Forecast for

Grafton IL

  • Tonight

    Tonight: Mostly cloudy, then gradually becoming mostly clear, with a low around 64. Light and variable wind.

    Low: 64 °F

    Decreasing
    Clouds

  • Tuesday

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

    High: 86 °F

    Increasing
    Clouds

  • Tuesday Night

    Tuesday Night: A 40 percent chance of showers and thunderstorms, mainly after 1am.  Increasing clouds, with a low around 69. Southeast wind around 6 mph becoming north after midnight.

    Low: 69 °F

    Mostly Clear
    then Chance
    T-storms

  • Wednesday

    Wednesday: A 30 percent chance of showers and thunderstorms.  Mostly cloudy, with a high near 83. Southeast wind around 6 mph becoming northwest in the morning.

    High: 83 °F

    Chance
    T-storms

  • 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 mostly clear, with a low around 64. Light and variable wind.
Tuesday
Increasing clouds, with a high near 86. Calm wind becoming southwest around 6 mph in the morning.
Tuesday Night
A 40 percent chance of showers and thunderstorms, mainly after 1am. Increasing clouds, with a low around 69. Southeast wind around 6 mph becoming north after midnight.
Wednesday
A 30 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 83. Southeast wind around 6 mph becoming northwest in the morning.
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)
6:11 pm CDT Aug 17, 2026
9pm 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