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.

N/A

Humidity NA
Wind Speed NA
Barometer NA
Dewpoint N/A
Visibility NA
Last update *** Not a current observation ***
Extended Forecast for

Johnston City IL

Extreme Heat Warning September 2, 01:14am until September 5, 08:00pm
Click here for hazard details and duration
Extreme Heat Warning
  •  
    Extreme Heat Warning September 2, 01:14am until September 5, 08:00pm

    NOW until 8:00pm Sat

    Extreme Heat Warning

  • Overnight

    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 5 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 7 mph in the afternoon.

    High: 100 °F

    Hot

  • Thursday Night

    Thursday Night: Clear, with a low around 76. Light and variable wind.

    Low: 76 °F

    Clear

  • Friday

    Friday: Sunny and hot, with a high near 100. Light and variable wind.

    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 after 1pm. Mostly sunny and hot, with a high near 99. Calm wind becoming northwest around 5 mph in the afternoon.

    High: 99 °F

    Sunny then
    Slight Chance
    T-storms

Detailed Forecast

Overnight
Clear, with a low around 77. Calm 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 5 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 7 mph in the afternoon.
Thursday Night
Clear, with a low around 76. Light and variable wind.
Friday
Sunny and hot, with a high near 100. Light and variable wind.
Friday Night
Mostly clear, with a low around 75. Calm wind.
Saturday
A slight chance of showers and thunderstorms after 1pm. Mostly sunny and hot, with a high near 99. Calm wind becoming northwest around 5 mph in the afternoon.
Saturday Night
Partly cloudy, with a low around 73. Calm wind.
Sunday
Sunny, with a high near 95. Calm wind becoming northeast 5 to 7 mph in the afternoon.
Sunday Night
Mostly clear, with a low around 69. East northeast wind around 6 mph becoming calm in the evening.
Labor Day
Sunny, with a high near 95. Calm wind becoming east 5 to 7 mph in the afternoon.
Monday Night
Partly cloudy, with a low around 70. Northeast wind around 6 mph becoming light and variable in the evening.
Tuesday
Mostly sunny, with a high near 95. South wind 3 to 8 mph.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Johnston City IL
 37.82°N 88.91°W
Last Update:
12:41 am CDT Sep 2, 2026
Forecast Valid:
1am CDT Sep 2, 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