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

72°F

22°C

Humidity 90%
Wind Speed Calm
Barometer 30.05 in
Dewpoint 69°F (21°C)
Visibility 10.00 mi
Last update 4 Aug 9:55 pm CDT
Extended Forecast for

Simpson IL

  • Tonight

    Tonight: Clear, with a low around 64. Calm wind.

    Low: 64 °F

    Clear

  • Wednesday

    Wednesday: Patchy fog before 7am. Otherwise, sunny, with a high near 90. Calm wind becoming south around 5 mph.

    High: 90 °F

    Patchy Fog
    then Sunny

  • Wednesday Night

    Wednesday Night: Mostly clear, with a low around 69. Calm wind.

    Low: 69 °F

    Mostly Clear

  • Thursday

    Thursday: A 20 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 88. Calm wind becoming southwest around 5 mph.

    High: 88 °F

    Mostly Sunny
    then Slight
    Chance
    T-storms

  • Thursday Night

    Thursday Night: A 40 percent chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 71. Calm wind.

    Low: 71 °F

    Partly Cloudy
    then Chance
    T-storms

  • Friday

    Friday: A 50 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 88. Calm wind becoming west southwest around 6 mph in the afternoon.

    High: 88 °F

    Chance
    T-storms

  • Friday Night

    Friday Night: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 70. Calm wind.

    Low: 70 °F

    Chance
    T-storms

  • Saturday

    Saturday: A slight chance of showers and thunderstorms. Mostly sunny, with a high near 89. Calm wind becoming southwest around 5 mph.

    High: 89 °F

    Slight Chance
    T-storms

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 70. Calm wind.

    Low: 70 °F

    Mostly Clear

Detailed Forecast

Tonight
Clear, with a low around 64. Calm wind.
Wednesday
Patchy fog before 7am. Otherwise, sunny, with a high near 90. Calm wind becoming south around 5 mph.
Wednesday Night
Mostly clear, with a low around 69. Calm wind.
Thursday
A 20 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 88. Calm wind becoming southwest around 5 mph.
Thursday Night
A 40 percent chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 71. Calm wind.
Friday
A 50 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 88. Calm wind becoming west southwest around 6 mph in the afternoon.
Friday Night
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 70. Calm wind.
Saturday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 89. Calm wind becoming southwest around 5 mph.
Saturday Night
Mostly clear, with a low around 70. Calm wind.
Sunday
Sunny, with a high near 91. Calm wind becoming south southwest 5 to 8 mph in the morning.
Sunday Night
Mostly clear, with a low around 73. Light south wind.
Monday
Sunny, with a high near 93. Light south southwest wind increasing to 5 to 9 mph in the morning.
Monday Night
Mostly clear, with a low around 74. South southwest wind 3 to 7 mph.
Tuesday
Mostly sunny, with a high near 92. South southwest wind 5 to 8 mph.
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ABOUT THIS FORECAST

 
Point Forecast:
Simpson IL
 37.46°N 88.77°W
Last Update:
8:46 pm CDT Aug 4, 2026
Forecast Valid:
10pm CDT Aug 4, 2026-6pm CDT Aug 11, 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