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

82°F

28°C

Humidity 77%
Wind Speed SW 9 mph
Barometer 30.08 in (1017.9 mb)
Dewpoint 74°F (23°C)
Visibility 10.00 mi
Heat Index88°F (31°C)
Last update 16 Aug 7:54 am CDT
Extended Forecast for

Illiopolis IL

Heat Advisory August 16, 12:00pm until August 17, 08:00pm
Click here for hazard details and duration
Heat Advisory

  • Today

    Today: A 20 percent chance of showers and thunderstorms after 4pm. Sunny and hot, with a high near 95. Heat index values as high as 106. South southwest wind 6 to 8 mph.

    High: 95 °F

    Sunny then
    Slight Chance
    T-storms

  • Tonight

    Tonight: A 20 percent chance of showers and thunderstorms before 8pm. Partly cloudy, with a low around 74. South wind 3 to 5 mph.

    Low: 74 °F

    Slight Chance
    T-storms then
    Partly Cloudy

  • Sunday

    Sunday: A 20 percent chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 95. Heat index values as high as 107. Calm wind becoming southwest around 5 mph.

    High: 95 °F

    Mostly Sunny
    then Slight
    Chance
    T-storms

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 74. Calm wind becoming south southeast around 5 mph after midnight.

    Low: 74 °F

    Mostly Clear

  • Monday

    Monday: Sunny and hot, with a high near 96. South southwest wind 5 to 7 mph.

    High: 96 °F

    Hot

  • Monday Night

    Monday Night: Mostly clear, with a low around 73. South wind 3 to 5 mph.

    Low: 73 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 94. West northwest wind 5 to 8 mph.

    High: 94 °F

    Sunny

  • Tuesday Night

    Tuesday Night: A 30 percent chance of showers and thunderstorms before 1am. Partly cloudy, with a low around 70.

    Low: 70 °F

    Chance
    T-storms

  • Wednesday

    Wednesday: Partly sunny, with a high near 83.

    High: 83 °F

    Partly Sunny

Detailed Forecast

Today
A 20 percent chance of showers and thunderstorms after 4pm. Sunny and hot, with a high near 95. Heat index values as high as 106. South southwest wind 6 to 8 mph.
Tonight
A 20 percent chance of showers and thunderstorms before 8pm. Partly cloudy, with a low around 74. South wind 3 to 5 mph.
Sunday
A 20 percent chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 95. Heat index values as high as 107. Calm wind becoming southwest around 5 mph.
Sunday Night
Mostly clear, with a low around 74. Calm wind becoming south southeast around 5 mph after midnight.
Monday
Sunny and hot, with a high near 96. South southwest wind 5 to 7 mph.
Monday Night
Mostly clear, with a low around 73. South wind 3 to 5 mph.
Tuesday
Sunny, with a high near 94. West northwest wind 5 to 8 mph.
Tuesday Night
A 30 percent chance of showers and thunderstorms before 1am. Partly cloudy, with a low around 70.
Wednesday
Partly sunny, with a high near 83.
Wednesday Night
Partly cloudy, with a low around 64.
Thursday
Mostly sunny, with a high near 84.
Thursday Night
Mostly clear, with a low around 63.
Friday
Sunny, with a high near 86.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Illiopolis IL
 39.83°N 89.23°W (Elev. 568 ft)
Last Update:
7:41 am CDT Aug 16, 2025
Forecast Valid:
8am CDT Aug 16, 2025-6pm CDT Aug 22, 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