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

21°F

-6°C

Humidity 62%
Wind Speed SW 5 mph
Barometer 30.32 in (1027.7 mb)
Dewpoint 10°F (-12°C)
Visibility 10.00 mi
Wind Chill14°F (-10°C)
Last update 23 Feb 10:54 pm CST
Extended Forecast for

Illiopolis IL

  • Tonight

    Tonight: Partly cloudy, with a low around 18. Light southwest wind becoming south 5 to 9 mph after midnight. Winds could gust as high as 15 mph.

    Low: 18 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly cloudy, with a high near 48. Breezy, with a south wind 13 to 23 mph, with gusts as high as 31 mph.

    High: 48 °F

    Mostly Cloudy
    and Breezy

  • Tuesday Night

    Tuesday Night: Mostly cloudy, with a low around 27. South southwest wind 7 to 14 mph becoming northwest after midnight. Winds could gust as high as 21 mph.

    Low: 27 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: Mostly sunny, with a high near 45. Northwest wind 6 to 9 mph.

    High: 45 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: A chance of rain before 9pm, then rain and snow likely between 9pm and 3am, then snow likely after 3am. Mostly cloudy, with a low around 29. East northeast wind 6 to 10 mph, with gusts as high as 15 mph. Chance of precipitation is 70%. New snow accumulation of less than one inch possible.

    Low: 29 °F

    Rain/Snow
    Likely

  • Thursday

    Thursday: A chance of rain and snow before noon. Cloudy through mid morning, then gradual clearing, with a high near 43. East northeast wind 8 to 10 mph becoming north northwest in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 30%.

    High: 43 °F

    Chance
    Rain/Snow
    then Mostly
    Sunny

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 28. North northwest wind around 7 mph becoming south after midnight.

    Low: 28 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 59.

    High: 59 °F

    Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 36.

    Low: 36 °F

    Mostly Clear

Detailed Forecast

Tonight
Partly cloudy, with a low around 18. Light southwest wind becoming south 5 to 9 mph after midnight. Winds could gust as high as 15 mph.
Tuesday
Mostly cloudy, with a high near 48. Breezy, with a south wind 13 to 23 mph, with gusts as high as 31 mph.
Tuesday Night
Mostly cloudy, with a low around 27. South southwest wind 7 to 14 mph becoming northwest after midnight. Winds could gust as high as 21 mph.
Wednesday
Mostly sunny, with a high near 45. Northwest wind 6 to 9 mph.
Wednesday Night
A chance of rain before 9pm, then rain and snow likely between 9pm and 3am, then snow likely after 3am. Mostly cloudy, with a low around 29. East northeast wind 6 to 10 mph, with gusts as high as 15 mph. Chance of precipitation is 70%. New snow accumulation of less than one inch possible.
Thursday
A chance of rain and snow before noon. Cloudy through mid morning, then gradual clearing, with a high near 43. East northeast wind 8 to 10 mph becoming north northwest in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 30%.
Thursday Night
Mostly clear, with a low around 28. North northwest wind around 7 mph becoming south after midnight.
Friday
Sunny, with a high near 59.
Friday Night
Mostly clear, with a low around 36.
Saturday
Sunny, with a high near 58.
Saturday Night
Mostly cloudy, with a low around 27.
Sunday
A chance of rain and snow. Mostly cloudy, with a high near 42.
Sunday Night
A chance of rain and snow. Mostly cloudy, with a low around 25.
Monday
A chance of rain and snow. Mostly cloudy, with a high near 41.
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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:
10:21 pm CST Feb 23, 2026
Forecast Valid:
11pm CST Feb 23, 2026-6pm CST Mar 2, 2026
 
Forecast Discussion
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation