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.

A Few Clouds

87°F

31°C

Humidity 55%
Wind Speed SW 14 mph
Barometer 29.87 in (1010.9 mb)
Dewpoint 69°F (21°C)
Visibility 10.00 mi
Heat Index91°F (33°C)
Last update 6 Jun 5:54 pm CDT
Extended Forecast for

Illiopolis IL

  • Tonight

    Tonight: A slight chance of showers and thunderstorms between 8pm and midnight. Mostly cloudy, with a low around 71. Southwest wind 5 to 9 mph becoming calm after midnight. Winds could gust as high as 15 mph. Chance of precipitation is 20%.

    Low: 71 °F

    Slight Chance
    T-storms then
    Mostly Cloudy

  • Sunday

    Sunday: A slight chance of showers and thunderstorms before 9am, then a chance of showers between 9am and 10am, then a chance of showers and thunderstorms after 10am. Partly sunny, with a high near 86. Light south wind becoming south southeast 5 to 10 mph in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 50%.

    High: 86 °F

    Chance
    Showers then
    Chance
    T-storms

  • Sunday Night

    Sunday Night: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 69. Southeast wind 8 to 10 mph, with gusts as high as 15 mph.

    Low: 69 °F

    Chance
    T-storms

  • Monday

    Monday: Showers likely, then showers and possibly a thunderstorm after 1pm. High near 84. South wind 11 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.

    High: 84 °F

    Showers
    Likely then
    Showers

  • Monday Night

    Monday Night: Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 69. South wind 7 to 11 mph, with gusts as high as 16 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

    Low: 69 °F

    Showers
    Likely

  • Tuesday

    Tuesday: A 30 percent chance of showers before 1pm. Partly sunny, with a high near 89. Southwest wind 7 to 10 mph, with gusts as high as 15 mph.

    High: 89 °F

    Chance
    Showers

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 73. South wind 7 to 9 mph.

    Low: 73 °F

    Partly Cloudy

  • Wednesday

    Wednesday: Sunny and hot, with a high near 95.

    High: 95 °F

    Hot

  • Wednesday Night

    Wednesday Night: Mostly clear, with a low around 74.

    Low: 74 °F

    Mostly Clear

Detailed Forecast

Tonight
A slight chance of showers and thunderstorms between 8pm and midnight. Mostly cloudy, with a low around 71. Southwest wind 5 to 9 mph becoming calm after midnight. Winds could gust as high as 15 mph. Chance of precipitation is 20%.
Sunday
A slight chance of showers and thunderstorms before 9am, then a chance of showers between 9am and 10am, then a chance of showers and thunderstorms after 10am. Partly sunny, with a high near 86. Light south wind becoming south southeast 5 to 10 mph in the afternoon. Winds could gust as high as 15 mph. Chance of precipitation is 50%.
Sunday Night
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 69. Southeast wind 8 to 10 mph, with gusts as high as 15 mph.
Monday
Showers likely, then showers and possibly a thunderstorm after 1pm. High near 84. South wind 11 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.
Monday Night
Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 69. South wind 7 to 11 mph, with gusts as high as 16 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Tuesday
A 30 percent chance of showers before 1pm. Partly sunny, with a high near 89. Southwest wind 7 to 10 mph, with gusts as high as 15 mph.
Tuesday Night
Partly cloudy, with a low around 73. South wind 7 to 9 mph.
Wednesday
Sunny and hot, with a high near 95.
Wednesday Night
Mostly clear, with a low around 74.
Thursday
A 30 percent chance of showers before 1pm. Mostly sunny, with a high near 93.
Thursday Night
A chance of showers and thunderstorms. Mostly clear, with a low around 70.
Friday
Mostly sunny, with a high near 92.
Friday Night
A chance of showers and thunderstorms. Partly cloudy, with a low around 68.
Saturday
Mostly sunny, with a high near 88.
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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:
5:51 pm CDT Jun 6, 2026
Forecast Valid:
6pm CDT Jun 6, 2026-6pm CDT Jun 13, 2026
 
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