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.

Fair

66°F

19°C

Humidity 81%
Wind Speed Calm
Barometer 30.05 in (1016.9 mb)
Dewpoint 60°F (16°C)
Visibility 10.00 mi
Last update 19 Sep 6:54 am CDT
Extended Forecast for

Illiopolis IL

  • Today

    Today: A slight chance of showers and thunderstorms before 9am, then a slight chance of showers and thunderstorms after 3pm. Partly sunny, with a high near 86. Light and variable wind becoming south southeast around 6 mph in the morning. Chance of precipitation is 20%.

    High: 86 °F

    Slight Chance
    T-storms

  • Tonight

    Tonight: A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 63. Southwest wind around 5 mph becoming calm in the evening.

    Low: 63 °F

    Chance
    T-storms

  • Saturday

    Saturday: A slight chance of showers and thunderstorms before 7am, then a slight chance of showers between 7am and 4pm, then a slight chance of showers and thunderstorms after 4pm. Mostly sunny, with a high near 86. Calm wind becoming south around 6 mph in the morning. Chance of precipitation is 20%.

    High: 86 °F

    Slight Chance
    T-storms

  • Saturday Night

    Saturday Night: A 40 percent chance of showers. Mostly cloudy, with a low around 64. South southeast wind 3 to 5 mph.

    Low: 64 °F

    Chance
    Showers

  • Sunday

    Sunday: A chance of showers before 1pm, then a chance of showers and thunderstorms between 1pm and 4pm, then a chance of showers after 4pm. Mostly cloudy, with a high near 82. Southwest wind 5 to 10 mph. Chance of precipitation is 30%.

    High: 82 °F

    Chance
    Showers then
    Chance
    T-storms

  • Sunday Night

    Sunday Night: A chance of showers before 1am, then showers likely and possibly a thunderstorm between 1am and 4am, then showers likely after 4am. Mostly cloudy, with a low around 64. South wind around 6 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 64 °F

    Showers
    Likely

  • Monday

    Monday: A 50 percent chance of showers. Partly sunny, with a high near 81. South southwest wind 6 to 10 mph, with gusts as high as 15 mph.

    High: 81 °F

    Chance
    Showers

  • Monday Night

    Monday Night: A 40 percent chance of showers. Mostly cloudy, with a low around 63.

    Low: 63 °F

    Chance
    Showers

  • Tuesday

    Tuesday: A chance of showers, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 80. Chance of precipitation is 40%.

    High: 80 °F

    Chance
    Showers then
    Chance
    T-storms

Detailed Forecast

Today
A slight chance of showers and thunderstorms before 9am, then a slight chance of showers and thunderstorms after 3pm. Partly sunny, with a high near 86. Light and variable wind becoming south southeast around 6 mph in the morning. Chance of precipitation is 20%.
Tonight
A 40 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 63. Southwest wind around 5 mph becoming calm in the evening.
Saturday
A slight chance of showers and thunderstorms before 7am, then a slight chance of showers between 7am and 4pm, then a slight chance of showers and thunderstorms after 4pm. Mostly sunny, with a high near 86. Calm wind becoming south around 6 mph in the morning. Chance of precipitation is 20%.
Saturday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 64. South southeast wind 3 to 5 mph.
Sunday
A chance of showers before 1pm, then a chance of showers and thunderstorms between 1pm and 4pm, then a chance of showers after 4pm. Mostly cloudy, with a high near 82. Southwest wind 5 to 10 mph. Chance of precipitation is 30%.
Sunday Night
A chance of showers before 1am, then showers likely and possibly a thunderstorm between 1am and 4am, then showers likely after 4am. Mostly cloudy, with a low around 64. South wind around 6 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Monday
A 50 percent chance of showers. Partly sunny, with a high near 81. South southwest wind 6 to 10 mph, with gusts as high as 15 mph.
Monday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 63.
Tuesday
A chance of showers, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 80. Chance of precipitation is 40%.
Tuesday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 63.
Wednesday
A chance of showers. Partly sunny, with a high near 77.
Wednesday Night
A chance of showers. Mostly cloudy, with a low around 61.
Thursday
A chance of showers. Partly sunny, with a high near 77.
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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:
6:55 am CDT Sep 19, 2025
Forecast Valid:
7am CDT Sep 19, 2025-6pm CDT Sep 25, 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