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

50°F

10°C

Humidity 80%
Wind Speed SW 6 mph
Barometer 30.06 in (1017.9 mb)
Dewpoint 44°F (7°C)
Visibility 10.00 mi
Wind Chill48°F (9°C)
Last update 10 Nov 1:54 am CST
Extended Forecast for

Illiopolis IL

  • Overnight

    Overnight: Clear, with a low around 45. West southwest wind around 6 mph, with gusts as high as 15 mph.

    Low: 45 °F

    Clear

  • Tuesday

    Tuesday: Sunny, with a high near 68. West northwest wind around 6 mph becoming light and variable in the afternoon.

    High: 68 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Increasing clouds, with a low around 43. Light and variable wind.

    Low: 43 °F

    Increasing
    Clouds

  • Veterans Day

    Veterans Day: Mostly sunny, with a high near 65. South wind 5 to 15 mph becoming northwest in the afternoon. Winds could gust as high as 24 mph.

    High: 65 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 38. North northwest wind 11 to 17 mph, with gusts as high as 23 mph.

    Low: 38 °F

    Partly Cloudy

  • Thursday

    Thursday: Partly sunny, with a high near 48. North northwest wind 11 to 17 mph, with gusts as high as 23 mph.

    High: 48 °F

    Partly Sunny

  • Thursday Night

    Thursday Night: Partly cloudy, with a low around 29. North northwest wind 8 to 14 mph, with gusts as high as 18 mph.

    Low: 29 °F

    Partly Cloudy

  • Friday

    Friday: Sunny, with a high near 43.

    High: 43 °F

    Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 23.

    Low: 23 °F

    Mostly Clear

Detailed Forecast

Overnight
Clear, with a low around 45. West southwest wind around 6 mph, with gusts as high as 15 mph.
Tuesday
Sunny, with a high near 68. West northwest wind around 6 mph becoming light and variable in the afternoon.
Tuesday Night
Increasing clouds, with a low around 43. Light and variable wind.
Veterans Day
Mostly sunny, with a high near 65. South wind 5 to 15 mph becoming northwest in the afternoon. Winds could gust as high as 24 mph.
Wednesday Night
Partly cloudy, with a low around 38. North northwest wind 11 to 17 mph, with gusts as high as 23 mph.
Thursday
Partly sunny, with a high near 48. North northwest wind 11 to 17 mph, with gusts as high as 23 mph.
Thursday Night
Partly cloudy, with a low around 29. North northwest wind 8 to 14 mph, with gusts as high as 18 mph.
Friday
Sunny, with a high near 43.
Friday Night
Mostly clear, with a low around 23.
Saturday
Sunny, with a high near 46.
Saturday Night
Mostly clear, with a low around 28.
Sunday
Mostly sunny, with a high near 51.
Sunday Night
Partly cloudy, with a low around 33.
Monday
Mostly sunny, with a high near 55.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Illiopolis IL
 39.85°N 89.26°W (Elev. 607 ft)
Last Update:
2:11 am CST Nov 10, 2026
Forecast Valid:
2am CST Nov 10, 2026-6pm CST Nov 16, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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