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

Hazardous Weather Conditions

Current conditions at

Decatur Airport (KDEC)

Lat: 39.83°NLon: 88.87°WElev: 670ft.

Overcast

74°F

23°C

Humidity 71%
Wind Speed SW 7 mph
Barometer 29.93 in (1013.1 mb)
Dewpoint 64°F (18°C)
Visibility 10.00 mi
Last update 22 Sep 12:54 pm CDT
Extended Forecast for

Harristown IL

  • This Afternoon

    This Afternoon: A 20 percent chance of showers and thunderstorms before 2pm. Mostly cloudy, with a high near 78. South wind around 8 mph.

    High: 78 °F

    Slight Chance
    T-storms

  • Tonight

    Tonight: Patchy fog after 3am. Otherwise, mostly cloudy, with a low around 63. South wind around 5 mph becoming calm in the evening.

    Low: 63 °F

    Mostly Cloudy
    then Patchy
    Fog

  • Tuesday

    Tuesday: A slight chance of showers between 10am and 1pm, then scattered showers and thunderstorms after 1pm. Areas of fog before 10am. Otherwise, partly sunny, with a high near 83. Calm wind becoming south 5 to 7 mph in the morning. Chance of precipitation is 30%.

    High: 83 °F

    Slight Chance
    Showers and
    Areas Fog
    then
    Scattered
    T-storms

  • Tuesday Night

    Tuesday Night: Showers likely and possibly a thunderstorm before 10pm, then showers likely between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 64. Light and variable wind becoming east around 6 mph after midnight. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

    Low: 64 °F

    Showers
    Likely

  • Wednesday

    Wednesday: Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 75. East northeast wind 7 to 11 mph, with gusts as high as 16 mph. Chance of precipitation is 70%. New rainfall amounts between a half and three quarters of an inch possible.

    High: 75 °F

    Showers
    Likely

  • Wednesday Night

    Wednesday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 60. North wind 7 to 10 mph. Chance of precipitation is 50%.

    Low: 60 °F

    Chance
    T-storms then
    Chance
    Showers

  • Thursday

    Thursday: A 40 percent chance of showers. Partly sunny, with a high near 72. West northwest wind 9 to 11 mph, with gusts as high as 16 mph.

    High: 72 °F

    Chance
    Showers

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 57.

    Low: 57 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 77.

    High: 77 °F

    Mostly Sunny

Detailed Forecast

This Afternoon
A 20 percent chance of showers and thunderstorms before 2pm. Mostly cloudy, with a high near 78. South wind around 8 mph.
Tonight
Patchy fog after 3am. Otherwise, mostly cloudy, with a low around 63. South wind around 5 mph becoming calm in the evening.
Tuesday
A slight chance of showers between 10am and 1pm, then scattered showers and thunderstorms after 1pm. Areas of fog before 10am. Otherwise, partly sunny, with a high near 83. Calm wind becoming south 5 to 7 mph in the morning. Chance of precipitation is 30%.
Tuesday Night
Showers likely and possibly a thunderstorm before 10pm, then showers likely between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 64. Light and variable wind becoming east around 6 mph after midnight. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.
Wednesday
Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 75. East northeast wind 7 to 11 mph, with gusts as high as 16 mph. Chance of precipitation is 70%. New rainfall amounts between a half and three quarters of an inch possible.
Wednesday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 60. North wind 7 to 10 mph. Chance of precipitation is 50%.
Thursday
A 40 percent chance of showers. Partly sunny, with a high near 72. West northwest wind 9 to 11 mph, with gusts as high as 16 mph.
Thursday Night
Partly cloudy, with a low around 57.
Friday
Mostly sunny, with a high near 77.
Friday Night
Mostly clear, with a low around 55.
Saturday
Sunny, with a high near 80.
Saturday Night
Mostly clear, with a low around 55.
Sunday
Sunny, with a high near 82.
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ABOUT THIS FORECAST

 
Point Forecast:
Harristown IL
 39.84°N 89.06°W (Elev. 699 ft)
Last Update:
12:40 pm CDT Sep 22, 2025
Forecast Valid:
1pm CDT Sep 22, 2025-6pm CDT Sep 28, 2025
 
Forecast Discussion
 
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Additional Resources

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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