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

41°F

5°C

Humidity 51%
Wind Speed SW 8 mph
Barometer 29.85 in (1011.4 mb)
Dewpoint 24°F (-4°C)
Visibility 10.00 mi
Wind Chill36°F (2°C)
Last update 11 Nov 5:54 pm CST
Extended Forecast for

Illiopolis IL

  • Tonight

    Tonight: Clear, with a low around 35. West wind 8 to 10 mph, with gusts as high as 22 mph.

    Low: 35 °F

    Clear

  • Wednesday

    Wednesday: Sunny, with a high near 59. West northwest wind 8 to 14 mph, with gusts as high as 23 mph.

    High: 59 °F

    Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 33. West wind 5 to 8 mph becoming calm after midnight.

    Low: 33 °F

    Partly Cloudy

  • Thursday

    Thursday: Partly sunny, with a high near 61. Calm wind becoming south 5 to 9 mph in the afternoon.

    High: 61 °F

    Partly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 44. South wind 6 to 8 mph.

    Low: 44 °F

    Partly Cloudy

  • Friday

    Friday: Mostly sunny, with a high near 70. South wind 6 to 10 mph, with gusts as high as 15 mph.

    High: 70 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 54. South wind 9 to 11 mph, with gusts as high as 18 mph.

    Low: 54 °F

    Partly Cloudy

  • Saturday

    Saturday: Mostly sunny, with a high near 75.

    High: 75 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 50.

    Low: 50 °F

    Partly Cloudy

Detailed Forecast

Tonight
Clear, with a low around 35. West wind 8 to 10 mph, with gusts as high as 22 mph.
Wednesday
Sunny, with a high near 59. West northwest wind 8 to 14 mph, with gusts as high as 23 mph.
Wednesday Night
Partly cloudy, with a low around 33. West wind 5 to 8 mph becoming calm after midnight.
Thursday
Partly sunny, with a high near 61. Calm wind becoming south 5 to 9 mph in the afternoon.
Thursday Night
Partly cloudy, with a low around 44. South wind 6 to 8 mph.
Friday
Mostly sunny, with a high near 70. South wind 6 to 10 mph, with gusts as high as 15 mph.
Friday Night
Partly cloudy, with a low around 54. South wind 9 to 11 mph, with gusts as high as 18 mph.
Saturday
Mostly sunny, with a high near 75.
Saturday Night
Partly cloudy, with a low around 50.
Sunday
Mostly sunny, with a high near 63.
Sunday Night
Mostly clear, with a low around 37.
Monday
A chance of rain. Partly sunny, with a high near 55.
Monday Night
A chance of rain. Mostly cloudy, with a low around 40.
Tuesday
Partly sunny, with a high near 54.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Illiopolis IL
 39.85°N 89.26°W (Elev. 607 ft)
Last Update:
5:32 pm CST Nov 11, 2025
Forecast Valid:
6pm CST Nov 11, 2025-6pm CST Nov 18, 2025
 
Forecast Discussion
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation