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

Decatur Airport (KDEC)

Lat: 39.83°NLon: 88.87°WElev: 670ft.

Fair

59°F

15°C

Humidity 33%
Wind Speed S 7 mph
Barometer 30.26 in (1024.8 mb)
Dewpoint 30°F (-1°C)
Visibility 10.00 mi
Last update 20 Apr 3:54 pm CDT
Extended Forecast for

Harristown IL

  • Tonight

    Tonight: Increasing clouds, with a low around 48. South southeast wind 8 to 14 mph, with gusts as high as 20 mph.

    Low: 48 °F

    Increasing
    Clouds

  • Tuesday

    Tuesday: Mostly sunny, with a high near 78. Breezy, with a southwest wind 13 to 22 mph, with gusts as high as 32 mph.

    High: 78 °F

    Mostly Sunny
    then Sunny
    and Breezy

  • Tuesday Night

    Tuesday Night: A 40 percent chance of showers and thunderstorms. Partly cloudy, with a low around 58. West southwest wind 13 to 16 mph, with gusts as high as 24 mph.

    Low: 58 °F

    Chance
    T-storms

  • Wednesday

    Wednesday: Mostly sunny, with a high near 77. West southwest wind around 11 mph, with gusts as high as 17 mph.

    High: 77 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Mostly clear, with a low around 56. South wind around 9 mph, with gusts as high as 15 mph.

    Low: 56 °F

    Mostly Clear

  • Thursday

    Thursday: Mostly sunny, with a high near 80. Breezy, with a south wind 10 to 15 mph increasing to 17 to 22 mph in the afternoon. Winds could gust as high as 30 mph.

    High: 80 °F

    Sunny then
    Mostly Sunny
    and Breezy

  • Thursday Night

    Thursday Night: Showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 61. Breezy, with a south wind 17 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 61 °F

    Partly Cloudy
    and Breezy
    then Showers
    Likely

  • Friday

    Friday: Showers and possibly a thunderstorm. High near 74. Chance of precipitation is 80%.

    High: 74 °F

    Showers

  • Friday Night

    Friday Night: A 50 percent chance of showers. Mostly cloudy, with a low around 51.

    Low: 51 °F

    Chance
    Showers

Detailed Forecast

Tonight
Increasing clouds, with a low around 48. South southeast wind 8 to 14 mph, with gusts as high as 20 mph.
Tuesday
Mostly sunny, with a high near 78. Breezy, with a southwest wind 13 to 22 mph, with gusts as high as 32 mph.
Tuesday Night
A 40 percent chance of showers and thunderstorms. Partly cloudy, with a low around 58. West southwest wind 13 to 16 mph, with gusts as high as 24 mph.
Wednesday
Mostly sunny, with a high near 77. West southwest wind around 11 mph, with gusts as high as 17 mph.
Wednesday Night
Mostly clear, with a low around 56. South wind around 9 mph, with gusts as high as 15 mph.
Thursday
Mostly sunny, with a high near 80. Breezy, with a south wind 10 to 15 mph increasing to 17 to 22 mph in the afternoon. Winds could gust as high as 30 mph.
Thursday Night
Showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 61. Breezy, with a south wind 17 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Friday
Showers and possibly a thunderstorm. High near 74. Chance of precipitation is 80%.
Friday Night
A 50 percent chance of showers. Mostly cloudy, with a low around 51.
Saturday
Mostly sunny, with a high near 70.
Saturday Night
Mostly cloudy, with a low around 49.
Sunday
Partly sunny, with a high near 69.
Sunday Night
A chance of showers. Mostly cloudy, with a low around 51.
Monday
A chance of showers. Mostly cloudy, with a high near 69.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Harristown IL
 39.84°N 89.06°W (Elev. 699 ft)
Last Update:
2:56 pm CDT Apr 20, 2026
Forecast Valid:
4pm CDT Apr 20, 2026-6pm CDT Apr 27, 2026
 
Forecast Discussion
 
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Additional Resources

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Hourly Weather Forecast

National Digital Forecast Database

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation