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

74°F

23°C

Humidity 96%
Wind Speed SE 5 mph
Barometer 30.10 in
Dewpoint 73°F (23°C)
Visibility 10.00 mi
Last update 3 Jul 2:55 am CDT
Extended Forecast for

Johnston City IL

Heat Advisory July 3, 08:00pm until July 4, 08:00pm
Extreme Heat Warning July 3, 03:19am until July 3, 08:00pm
Click here for hazard details and duration
Heat Advisory
Extreme Heat Warning
  •  
    Extreme Heat Warning July 3, 03:19am until July 3, 08:00pm

    NOW until 8:00pm Fri

    Extreme Heat Warning

  • Overnight

    Low: 76 °F

    Mostly Clear

  • Friday

    Friday: Mostly sunny, with a high near 96. Heat index values as high as 106. Calm wind becoming south southwest 5 to 7 mph in the afternoon.

    High: 96 °F

    Mostly Sunny

  • Friday Night

    Friday Night: Mostly clear, with a low around 75. South wind around 5 mph becoming calm in the evening.

    Low: 75 °F

    Mostly Clear

  • Independence Day

    Independence Day: A 30 percent chance of showers and thunderstorms, mainly after 5pm. Mostly sunny, with a high near 94. Calm wind becoming south southwest around 6 mph in the afternoon.

    High: 94 °F

    Sunny then
    Chance
    T-storms

  • Saturday Night

    Saturday Night: A chance of showers and thunderstorms before 10pm, then a slight chance of showers between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 74. Light south southwest wind. Chance of precipitation is 30%.

    Low: 74 °F

    Chance
    T-storms then
    Chance
    Showers

  • Sunday

    Sunday: A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 93. Calm wind becoming west around 5 mph in the afternoon.

    High: 93 °F

    Chance
    Showers then
    Chance
    T-storms

  • Sunday Night

    Sunday Night: A chance of showers and thunderstorms before 1am, then a slight chance of showers. Partly cloudy, with a low around 72. Calm wind. Chance of precipitation is 50%.

    Low: 72 °F

    Chance
    T-storms then
    Chance
    Showers

  • Monday

    Monday: A slight chance of showers, then a chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 90. Calm wind becoming northwest around 5 mph in the afternoon.

    High: 90 °F

    Chance
    Showers

Detailed Forecast

Overnight
Mostly clear, with a low around 76. Calm wind.
Friday
Mostly sunny, with a high near 96. Heat index values as high as 106. Calm wind becoming south southwest 5 to 7 mph in the afternoon.
Friday Night
Mostly clear, with a low around 75. South wind around 5 mph becoming calm in the evening.
Independence Day
A 30 percent chance of showers and thunderstorms, mainly after 5pm. Mostly sunny, with a high near 94. Calm wind becoming south southwest around 6 mph in the afternoon.
Saturday Night
A chance of showers and thunderstorms before 10pm, then a slight chance of showers between 10pm and 1am, then a chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 74. Light south southwest wind. Chance of precipitation is 30%.
Sunday
A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 93. Calm wind becoming west around 5 mph in the afternoon.
Sunday Night
A chance of showers and thunderstorms before 1am, then a slight chance of showers. Partly cloudy, with a low around 72. Calm wind. Chance of precipitation is 50%.
Monday
A slight chance of showers, then a chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 90. Calm wind becoming northwest around 5 mph in the afternoon.
Monday Night
A chance of showers and thunderstorms before 1am, then a slight chance of showers. Partly cloudy, with a low around 71. Light north northeast wind.
Tuesday
A slight chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 90. Calm wind becoming north around 6 mph in the afternoon.
Tuesday Night
Partly cloudy, with a low around 72. Light north wind.
Wednesday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 91. Light and variable wind.
Wednesday Night
Partly cloudy, with a low around 72. Calm wind.
Thursday
A chance of showers and thunderstorms. Mostly sunny, with a high near 92. Calm wind becoming south southwest 5 to 7 mph in the morning.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Johnston City IL
 37.82°N 88.91°W
Last Update:
2:16 am CDT Jul 3, 2026
Forecast Valid:
3am CDT Jul 3, 2026-6pm CDT Jul 9, 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