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

Marion - Williamson County Regional Airport (KMWA)

Lat: 37.77°NLon: 89.01°WElev: 486ft.

Fair

88°F

31°C

Humidity 31%
Wind Speed NE 6 mph
Barometer 30.03 in
Dewpoint 54°F (12°C)
Visibility 10.00 mi
Heat Index86°F (30°C)
Last update 7 Sep 5:45 pm CDT
Extended Forecast for

Johnston City IL

  • Tonight

    Tonight: Mostly clear, with a low around 63. East wind around 5 mph becoming calm in the evening.

    Low: 63 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 96. Calm wind becoming south 5 to 7 mph in the morning.

    High: 96 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 73. Light south southeast wind becoming south 5 to 10 mph after midnight.

    Low: 73 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny and hot, with a high near 99. Heat index values as high as 105. Southwest wind 10 to 14 mph, with gusts as high as 20 mph.

    High: 99 °F

    Hot

  • Wednesday Night

    Wednesday Night: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Partly cloudy, with a low around 72. South wind 3 to 7 mph. Chance of precipitation is 70%.

    Low: 72 °F

    Chance
    Showers then
    Showers
    Likely

  • Thursday

    Thursday: Showers and possibly a thunderstorm. High near 86. Calm wind becoming west northwest 5 to 7 mph in the morning. Chance of precipitation is 90%.

    High: 86 °F

    Showers

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms before 1am, then a slight chance of showers. Mostly cloudy, with a low around 65. Calm wind. Chance of precipitation is 30%.

    Low: 65 °F

    Chance
    Showers

  • Friday

    Friday: A slight chance of showers after 1pm. Mostly sunny, with a high near 88. Calm wind becoming south southwest around 5 mph in the afternoon.

    High: 88 °F

    Mostly Sunny
    then Slight
    Chance
    Showers

  • Friday Night

    Friday Night: A slight chance of showers after 1am. Partly cloudy, with a low around 67. Calm wind.

    Low: 67 °F

    Partly Cloudy
    then Slight
    Chance
    Showers

Detailed Forecast

Tonight
Mostly clear, with a low around 63. East wind around 5 mph becoming calm in the evening.
Tuesday
Sunny, with a high near 96. Calm wind becoming south 5 to 7 mph in the morning.
Tuesday Night
Mostly clear, with a low around 73. Light south southeast wind becoming south 5 to 10 mph after midnight.
Wednesday
Sunny and hot, with a high near 99. Heat index values as high as 105. Southwest wind 10 to 14 mph, with gusts as high as 20 mph.
Wednesday Night
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Partly cloudy, with a low around 72. South wind 3 to 7 mph. Chance of precipitation is 70%.
Thursday
Showers and possibly a thunderstorm. High near 86. Calm wind becoming west northwest 5 to 7 mph in the morning. Chance of precipitation is 90%.
Thursday Night
A chance of showers and thunderstorms before 1am, then a slight chance of showers. Mostly cloudy, with a low around 65. Calm wind. Chance of precipitation is 30%.
Friday
A slight chance of showers after 1pm. Mostly sunny, with a high near 88. Calm wind becoming south southwest around 5 mph in the afternoon.
Friday Night
A slight chance of showers after 1am. Partly cloudy, with a low around 67. Calm wind.
Saturday
A chance of showers, with thunderstorms also possible after 1pm. Mostly sunny, with a high near 92. Calm wind becoming southwest 5 to 7 mph in the morning.
Saturday Night
A slight chance of showers. Mostly clear, with a low around 67. Calm wind.
Sunday
Sunny, with a high near 92. Calm wind becoming south 5 to 8 mph in the morning.
Sunday Night
Mostly clear, with a low around 66. Calm wind becoming south around 5 mph after midnight.
Monday
Sunny, with a high near 91. Southwest wind 5 to 10 mph.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Johnston City IL
 37.82°N 88.91°W
Last Update:
4:50 pm CDT Sep 7, 2026
Forecast Valid:
6pm CDT Sep 7, 2026-6pm CDT Sep 14, 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