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.

Fog/Mist

80°F

27°C

Humidity 94%
Wind Speed S 5 mph
Barometer 29.88 in (1011.1 mb)
Dewpoint 78°F (26°C)
Visibility 5.00 mi
Heat Index86°F (30°C)
Last update 27 Jul 12:54 am CDT
Extended Forecast for

Harristown IL

Heat Advisory July 27, 01:19am until July 27, 09:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory July 27, 01:19am until July 27, 09:00pm

    NOW until 9:00pm Mon

    Heat Advisory

  • Overnight

    Low: 75 °F

    Patchy Fog

  • Monday

    Monday: Patchy fog before 8am. Otherwise, sunny, with a high near 92. Heat index values as high as 107. South southwest wind 7 to 14 mph, with gusts as high as 20 mph.

    High: 92 °F

    Patchy Fog
    then Sunny

  • Monday Night

    Monday Night: Increasing clouds, with a low around 74. Southwest wind 8 to 11 mph becoming north northwest after midnight. Winds could gust as high as 17 mph.

    Low: 74 °F

    Increasing
    Clouds

  • Tuesday

    Tuesday: Mostly cloudy, then gradually becoming sunny, with a high near 86. North wind 10 to 14 mph, with gusts as high as 18 mph.

    High: 86 °F

    Decreasing
    Clouds

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 63. North northeast wind 5 to 10 mph, with gusts as high as 15 mph.

    Low: 63 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 84. North northeast wind 6 to 9 mph.

    High: 84 °F

    Sunny

  • Wednesday Night

    Wednesday Night: Clear, with a low around 63. North northeast wind 5 to 7 mph becoming calm in the evening.

    Low: 63 °F

    Clear

  • Thursday

    Thursday: Sunny, with a high near 85.

    High: 85 °F

    Sunny

Detailed Forecast

Overnight
Patchy fog. Otherwise, mostly cloudy, with a low around 75. South southeast wind around 5 mph.
Monday
Patchy fog before 8am. Otherwise, sunny, with a high near 92. Heat index values as high as 107. South southwest wind 7 to 14 mph, with gusts as high as 20 mph.
Monday Night
Increasing clouds, with a low around 74. Southwest wind 8 to 11 mph becoming north northwest after midnight. Winds could gust as high as 17 mph.
Tuesday
Mostly cloudy, then gradually becoming sunny, with a high near 86. North wind 10 to 14 mph, with gusts as high as 18 mph.
Tuesday Night
Mostly clear, with a low around 63. North northeast wind 5 to 10 mph, with gusts as high as 15 mph.
Wednesday
Sunny, with a high near 84. North northeast wind 6 to 9 mph.
Wednesday Night
Clear, with a low around 63. North northeast wind 5 to 7 mph becoming calm in the evening.
Thursday
Sunny, with a high near 85.
Thursday Night
Partly cloudy, with a low around 66.
Friday
A 40 percent chance of showers. Partly sunny, with a high near 83.
Friday Night
A chance of showers. Mostly cloudy, with a low around 66.
Saturday
A chance of showers. Mostly sunny, with a high near 83.
Saturday Night
Mostly clear, with a low around 65.
Sunday
Sunny, with a high near 84.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Harristown IL
 39.84°N 89.06°W (Elev. 699 ft)
Last Update:
11:56 pm CDT Jul 26, 2026
Forecast Valid:
1am CDT Jul 27, 2026-6pm CDT Aug 2, 2026
 
Forecast Discussion
 
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Additional Resources

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Chance of Precipitation