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

95°F

35°C

Humidity 47%
Wind Speed S 6 mph
Barometer 30.01 in
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Heat Index103°F (39°C)
Last update 18 Aug 3:45 pm CDT
Extended Forecast for

3 Miles ENE Johnston City IL

Heat Advisory August 18, 04:03pm until August 19, 07:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 18, 04:03pm until August 19, 07:00pm

    NOW until 7:00pm Tue

    Heat Advisory

  • This Afternoon

    High: 98 °F

    Hot

  • Tonight

    Tonight: Clear, with a low around 76. Calm wind.

    Low: 76 °F

    Clear

  • Tuesday

    Tuesday: A 40 percent chance of showers and thunderstorms, mainly after 4pm. Sunny and hot, with a high near 97. Heat index values as high as 105. Calm wind becoming west around 5 mph.

    High: 97 °F

    Sunny then
    Chance
    T-storms

  • Tuesday Night

    Tuesday Night: A 50 percent chance of showers and thunderstorms. Partly cloudy, with a low around 72. Calm wind.

    Low: 72 °F

    Chance
    T-storms

  • Wednesday

    Wednesday: A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 90. Calm wind becoming north northeast 5 to 9 mph in the morning.

    High: 90 °F

    Chance
    T-storms

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 69. North northeast wind 5 to 8 mph.

    Low: 69 °F

    Partly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 89. North northeast wind 6 to 9 mph.

    High: 89 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 67. North northeast wind 5 to 7 mph becoming calm in the evening.

    Low: 67 °F

    Mostly Clear

Detailed Forecast

This Afternoon
Sunny and hot, with a high near 98. Calm wind.
Tonight
Clear, with a low around 76. Calm wind.
Tuesday
A 40 percent chance of showers and thunderstorms, mainly after 4pm. Sunny and hot, with a high near 97. Heat index values as high as 105. Calm wind becoming west around 5 mph.
Tuesday Night
A 50 percent chance of showers and thunderstorms. Partly cloudy, with a low around 72. Calm wind.
Wednesday
A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 90. Calm wind becoming north northeast 5 to 9 mph in the morning.
Wednesday Night
Partly cloudy, with a low around 69. North northeast wind 5 to 8 mph.
Thursday
Mostly sunny, with a high near 89. North northeast wind 6 to 9 mph.
Thursday Night
Mostly clear, with a low around 67. North northeast wind 5 to 7 mph becoming calm in the evening.
Friday
Sunny, with a high near 91. Calm wind becoming north northeast around 6 mph in the afternoon.
Friday Night
Mostly clear, with a low around 67. Light north northeast wind.
Saturday
Sunny, with a high near 90. Calm wind becoming north northwest 5 to 7 mph in the afternoon.
Saturday Night
Mostly clear, with a low around 64. North northwest wind around 6 mph becoming calm in the evening.
Sunday
Sunny, with a high near 85. Light north wind becoming north northwest 5 to 9 mph in the morning.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
3 Miles ENE Johnston City IL
 37.82°N 88.86°W
Last Update:
2:30 pm CDT Aug 18, 2025
Forecast Valid:
4pm CDT Aug 18, 2025-6pm CDT Aug 24, 2025
 
Forecast Discussion
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation