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

68°F

20°C

Humidity 81%
Wind Speed SW 5 mph
Barometer 30.02 in (1016.2 mb)
Dewpoint 62°F (17°C)
Visibility 7.00 mi
Last update 19 Jun 10:54 pm CDT
Extended Forecast for

Harristown IL

  • Tonight

    Tonight: Mostly cloudy, with a low around 62. Light and variable wind becoming south southwest around 5 mph after midnight.

    Low: 62 °F

    Mostly Cloudy

  • Saturday

    Saturday: Mostly sunny, with a high near 81. West northwest wind 3 to 7 mph.

    High: 81 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: A 30 percent chance of showers and thunderstorms after 4am. Partly cloudy, with a low around 61. Calm wind becoming east southeast around 6 mph after midnight.

    Low: 61 °F

    Partly Cloudy
    then Chance
    Showers

  • Sunday

    Sunday: A chance of showers before 7am, then showers and possibly a thunderstorm between 7am and 1pm, then showers and thunderstorms after 1pm. High near 76. East southeast wind 9 to 17 mph, with gusts as high as 25 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

    High: 76 °F

    Showers then
    T-storms

  • Sunday Night

    Sunday Night: Showers and thunderstorms, mainly before 1am. Low around 61. South wind 14 to 18 mph becoming north after midnight. Winds could gust as high as 23 mph. Chance of precipitation is 80%. New rainfall amounts between a half and three quarters of an inch possible.

    Low: 61 °F

    T-storms

  • Monday

    Monday: Partly sunny, with a high near 74. North wind around 15 mph, with gusts as high as 21 mph.

    High: 74 °F

    Partly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 55. Northeast wind 6 to 11 mph, with gusts as high as 16 mph.

    Low: 55 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 76.

    High: 76 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 58.

    Low: 58 °F

    Partly Cloudy

Detailed Forecast

Tonight
Mostly cloudy, with a low around 62. Light and variable wind becoming south southwest around 5 mph after midnight.
Saturday
Mostly sunny, with a high near 81. West northwest wind 3 to 7 mph.
Saturday Night
A 30 percent chance of showers and thunderstorms after 4am. Partly cloudy, with a low around 61. Calm wind becoming east southeast around 6 mph after midnight.
Sunday
A chance of showers before 7am, then showers and possibly a thunderstorm between 7am and 1pm, then showers and thunderstorms after 1pm. High near 76. East southeast wind 9 to 17 mph, with gusts as high as 25 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.
Sunday Night
Showers and thunderstorms, mainly before 1am. Low around 61. South wind 14 to 18 mph becoming north after midnight. Winds could gust as high as 23 mph. Chance of precipitation is 80%. New rainfall amounts between a half and three quarters of an inch possible.
Monday
Partly sunny, with a high near 74. North wind around 15 mph, with gusts as high as 21 mph.
Monday Night
Partly cloudy, with a low around 55. Northeast wind 6 to 11 mph, with gusts as high as 16 mph.
Tuesday
Mostly sunny, with a high near 76.
Tuesday Night
Partly cloudy, with a low around 58.
Wednesday
Mostly sunny, with a high near 77.
Wednesday Night
Mostly clear, with a low around 58.
Thursday
Mostly sunny, with a high near 77.
Thursday Night
A chance of showers. Partly cloudy, with a low around 58.
Friday
Mostly sunny, with a high near 79.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Harristown IL
 39.85°N 89.08°W (Elev. 653 ft)
Last Update:
10:16 pm CDT Jun 19, 2026
Forecast Valid:
11pm CDT Jun 19, 2026-6pm CDT Jun 26, 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