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

Hazardous Weather Conditions

Current conditions at

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

Lat: 38.93°NLon: 90.43°WElev: 436ft.

Fair

76°F

24°C

Humidity 88%
Wind Speed Calm
Barometer 29.99 in (1015.1 mb)
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Heat Index76°F (24°C)
Last update 17 Aug 11:54 pm CDT
Extended Forecast for

Grafton IL

Heat Advisory August 18, 12:55am until August 18, 08:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 18, 12:55am until August 18, 08:00pm

    NOW until 8:00pm Mon

    Heat Advisory

  • Overnight

    Low: 75 °F

    Mostly Clear

  • Monday

    Monday: Sunny, with a high near 95. Heat index values as high as 106. South wind 3 to 7 mph.

    High: 95 °F

    Sunny

  • Monday Night

    Monday Night: A 20 percent chance of showers and thunderstorms after 2am. Partly cloudy, with a low around 73. Southeast wind around 5 mph becoming calm after midnight.

    Low: 73 °F

    Partly Cloudy
    then Slight
    Chance
    T-storms

  • Tuesday

    Tuesday: A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91. Light and variable wind becoming west around 6 mph in the morning.

    High: 91 °F

    Chance
    T-storms

  • Tuesday Night

    Tuesday Night: A chance of showers and thunderstorms before 4am, then a slight chance of showers. Mostly cloudy, with a low around 73. North wind 3 to 5 mph. Chance of precipitation is 30%.

    Low: 73 °F

    Chance
    T-storms then
    Chance
    Showers

  • Wednesday

    Wednesday: A slight chance of showers, with thunderstorms also possible after 10am. Mostly sunny, with a high near 83. Chance of precipitation is 20%.

    High: 83 °F

    Slight Chance
    T-storms

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 66.

    Low: 66 °F

    Partly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 83.

    High: 83 °F

    Mostly Sunny

Detailed Forecast

Overnight
Mostly clear, with a low around 75. Light east wind.
Monday
Sunny, with a high near 95. Heat index values as high as 106. South wind 3 to 7 mph.
Monday Night
A 20 percent chance of showers and thunderstorms after 2am. Partly cloudy, with a low around 73. Southeast wind around 5 mph becoming calm after midnight.
Tuesday
A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91. Light and variable wind becoming west around 6 mph in the morning.
Tuesday Night
A chance of showers and thunderstorms before 4am, then a slight chance of showers. Mostly cloudy, with a low around 73. North wind 3 to 5 mph. Chance of precipitation is 30%.
Wednesday
A slight chance of showers, with thunderstorms also possible after 10am. Mostly sunny, with a high near 83. Chance of precipitation is 20%.
Wednesday Night
Partly cloudy, with a low around 66.
Thursday
Mostly sunny, with a high near 83.
Thursday Night
Mostly clear, with a low around 66.
Friday
Sunny, with a high near 86.
Friday Night
Mostly clear, with a low around 67.
Saturday
Sunny, with a high near 85.
Saturday Night
Mostly clear, with a low around 61.
Sunday
Sunny, with a high near 80.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Grafton IL
 38.98°N 90.44°W (Elev. 515 ft)
Last Update:
12:11 am CDT Aug 18, 2025
Forecast Valid:
12am CDT Aug 18, 2025-6pm CDT Aug 24, 2025
 
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