National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Hazardous Weather Conditions

Current conditions at

Marion - Williamson County Regional Airport (KMWA)

Lat: 37.77°NLon: 89.01°WElev: 486ft.

Fair

91°F

33°C

Humidity 52%
Wind Speed S 6 mph
Barometer 30.01 in
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Heat Index98°F (37°C)
Last update 1 Sep 6:45 pm CDT
Extended Forecast for

Johnston City IL

Extreme Heat Warning until September 5, 08:00pm
Click here for hazard details and duration
Extreme Heat Warning
  •  
    Extreme Heat Warning until September 5, 08:00pm

    NOW until 8:00pm Sat

    Extreme Heat Warning

  • Tonight

    Low: 77 °F

    Clear

  • Wednesday

    Wednesday: Sunny and hot, with a high near 100. Heat index values as high as 106. Calm wind becoming south southwest 5 to 8 mph in the morning.

    High: 100 °F

    Hot

  • Wednesday Night

    Wednesday Night: Clear, with a low around 77. South wind around 6 mph becoming calm in the evening.

    Low: 77 °F

    Clear

  • Thursday

    Thursday: Sunny and hot, with a high near 100. Heat index values as high as 106. Calm wind becoming southwest 5 to 8 mph in the afternoon.

    High: 100 °F

    Hot

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 77. Light and variable wind.

    Low: 77 °F

    Mostly Clear

  • Friday

    Friday: Sunny and hot, with a high near 100. Calm wind becoming southwest around 5 mph in the afternoon.

    High: 100 °F

    Hot

  • Friday Night

    Friday Night: Mostly clear, with a low around 75. Calm wind.

    Low: 75 °F

    Mostly Clear

  • Saturday

    Saturday: A slight chance of showers and thunderstorms. Mostly sunny and hot, with a high near 99. Calm wind becoming west northwest around 5 mph in the afternoon.

    High: 99 °F

    Slight Chance
    T-storms

Detailed Forecast

Tonight
Clear, with a low around 77. Light south wind.
Wednesday
Sunny and hot, with a high near 100. Heat index values as high as 106. Calm wind becoming south southwest 5 to 8 mph in the morning.
Wednesday Night
Clear, with a low around 77. South wind around 6 mph becoming calm in the evening.
Thursday
Sunny and hot, with a high near 100. Heat index values as high as 106. Calm wind becoming southwest 5 to 8 mph in the afternoon.
Thursday Night
Mostly clear, with a low around 77. Light and variable wind.
Friday
Sunny and hot, with a high near 100. Calm wind becoming southwest around 5 mph in the afternoon.
Friday Night
Mostly clear, with a low around 75. Calm wind.
Saturday
A slight chance of showers and thunderstorms. Mostly sunny and hot, with a high near 99. Calm wind becoming west northwest around 5 mph in the afternoon.
Saturday Night
Partly cloudy, with a low around 73. Calm wind.
Sunday
A slight chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 96. Calm wind becoming north northeast 5 to 8 mph in the afternoon.
Sunday Night
Mostly clear, with a low around 70. East northeast wind around 5 mph becoming calm in the evening.
Labor Day
Sunny, with a high near 94. Calm wind becoming east southeast 5 to 7 mph in the morning.
Monday Night
Partly cloudy, with a low around 68. East wind 3 to 6 mph.
Tuesday
Mostly sunny, with a high near 93. Light and variable wind becoming south southwest 5 to 8 mph in the morning.
Basemap Options
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Johnston City IL
 37.82°N 88.91°W
Last Update:
5:56 pm CDT Sep 1, 2026
Forecast Valid:
8pm CDT Sep 1, 2026-6pm CDT Sep 8, 2026
 
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