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

77°F

25°C

Humidity 91%
Wind Speed Calm
Barometer 30.02 in
Dewpoint 74°F (23°C)
Visibility 10.00 mi
Heat Index78°F (26°C)
Last update 18 Aug 1:55 am CDT
Extended Forecast for

4 Miles SW Simpson IL

Heat Advisory August 18, 02:10am until August 19, 07:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory August 18, 02:10am until August 19, 07:00pm

    NOW until 7:00pm Tue

    Heat Advisory

  • Overnight

    Low: 75 °F

    Mostly Clear

  • Monday

    Monday: Sunny and hot, with a high near 97. Heat index values as high as 105. Calm wind becoming east southeast around 5 mph.

    High: 97 °F

    Hot

  • Monday Night

    Monday Night: Mostly clear, with a low around 74. Light east wind.

    Low: 74 °F

    Mostly Clear

  • Tuesday

    Tuesday: A 30 percent chance of showers and thunderstorms after 1pm. Sunny and hot, with a high near 97. Calm wind.

    High: 97 °F

    Sunny then
    Chance
    T-storms

  • Tuesday Night

    Tuesday Night: A 40 percent chance of showers and thunderstorms. Partly cloudy, with a low around 73. Calm wind.

    Low: 73 °F

    Chance
    T-storms

  • Wednesday

    Wednesday: A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91. Calm wind becoming north around 6 mph in the afternoon.

    High: 91 °F

    Chance
    T-storms

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 68. North northeast wind around 6 mph becoming calm in the evening.

    Low: 68 °F

    Partly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 89. North northeast wind 5 to 7 mph.

    High: 89 °F

    Mostly Sunny

Detailed Forecast

Overnight
Mostly clear, with a low around 75. Calm wind.
Monday
Sunny and hot, with a high near 97. Heat index values as high as 105. Calm wind becoming east southeast around 5 mph.
Monday Night
Mostly clear, with a low around 74. Light east wind.
Tuesday
A 30 percent chance of showers and thunderstorms after 1pm. Sunny and hot, with a high near 97. Calm wind.
Tuesday Night
A 40 percent chance of showers and thunderstorms. Partly cloudy, with a low around 73. Calm wind.
Wednesday
A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91. Calm wind becoming north around 6 mph in the afternoon.
Wednesday Night
Partly cloudy, with a low around 68. North northeast wind around 6 mph becoming calm in the evening.
Thursday
Mostly sunny, with a high near 89. North northeast wind 5 to 7 mph.
Thursday Night
Mostly clear, with a low around 67. North northeast wind around 6 mph becoming calm in the evening.
Friday
Sunny, with a high near 91. Light north northeast wind.
Friday Night
Mostly clear, with a low around 67. Calm wind.
Saturday
Sunny, with a high near 91. Calm wind becoming northwest around 5 mph in the afternoon.
Saturday Night
Mostly clear, with a low around 65. Light north wind.
Sunday
Sunny, with a high near 86. Calm wind becoming north 5 to 7 mph in the afternoon.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
4 Miles SW Simpson IL
 37.44°N 88.82°W
Last Update:
1:45 am CDT Aug 18, 2025
Forecast Valid:
2am CDT Aug 18, 2025-6pm CDT Aug 24, 2025
 
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