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

81°F

27°C

Humidity 82%
Wind Speed S 10 mph
Barometer 30.08 in (1017.8 mb)
Dewpoint 75°F (24°C)
Visibility 10.00 mi
Heat Index87°F (31°C)
Last update 16 Aug 12:54 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

  • Overnight

    Overnight: A 20 percent chance of showers before 2am. Partly cloudy, with a low around 75. South wind around 6 mph.

    Low: 75 °F

    Slight Chance
    Showers

  • Saturday

    Saturday: Mostly sunny and hot, with a high near 95. Heat index values as high as 106. South southwest wind around 7 mph.

    High: 95 °F

    Hot

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 73. Light south wind.

    Low: 73 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny and hot, with a high near 96. Heat index values as high as 106. Southwest wind 3 to 5 mph.

    High: 96 °F

    Hot

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 74. South southeast wind 3 to 5 mph.

    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 74. South southwest wind 3 to 5 mph.

    Low: 74 °F

    Mostly Clear

  • Tuesday

    Tuesday: Mostly sunny, with a high near 94.

    High: 94 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 70.

    Low: 70 °F

    Partly Cloudy

Detailed Forecast

Overnight
A 20 percent chance of showers before 2am. Partly cloudy, with a low around 75. South wind around 6 mph.
Saturday
Mostly sunny and hot, with a high near 95. Heat index values as high as 106. South southwest wind around 7 mph.
Saturday Night
Mostly clear, with a low around 73. Light south wind.
Sunday
Sunny and hot, with a high near 96. Heat index values as high as 106. Southwest wind 3 to 5 mph.
Sunday Night
Mostly clear, with a low around 74. South southeast wind 3 to 5 mph.
Monday
Sunny and hot, with a high near 96. South southwest wind 5 to 7 mph.
Monday Night
Mostly clear, with a low around 74. South southwest wind 3 to 5 mph.
Tuesday
Mostly sunny, with a high near 94.
Tuesday Night
Partly cloudy, with a low around 70.
Wednesday
Mostly sunny, with a high near 85.
Wednesday Night
Mostly clear, with a low around 64.
Thursday
Sunny, with a high near 85.
Thursday Night
Mostly clear, with a low around 63.
Friday
Sunny, with a high near 87.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Illiopolis IL
 39.85°N 89.26°W (Elev. 607 ft)
Last Update:
1:41 am CDT Aug 16, 2025
Forecast Valid:
1am 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