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

54°F

12°C

Humidity 100%
Wind Speed Calm
Barometer 29.88 in
Dewpoint 54°F (12°C)
Visibility 10.00 mi
Last update 21 Mar 6:45 am CDT
Extended Forecast for

Simpson IL

  • Today

    Today: Sunny, with a high near 85. Calm wind becoming west southwest 5 to 7 mph in the morning.

    High: 85 °F

    Sunny

  • Tonight

    Tonight: Clear, with a low around 61. South southwest wind 5 to 8 mph.

    Low: 61 °F

    Clear

  • Sunday

    Sunday: Sunny, with a high near 85. South southwest wind 8 to 15 mph, with gusts as high as 26 mph.

    High: 85 °F

    Sunny

  • Sunday Night

    Sunday Night: A 30 percent chance of showers and thunderstorms before 1am. Mostly cloudy, then gradually becoming mostly clear, with a low around 40. Southwest wind 7 to 16 mph becoming north in the evening. Winds could gust as high as 26 mph.

    Low: 40 °F

    Chance
    T-storms

  • Monday

    Monday: Sunny, with a high near 60. North northeast wind around 9 mph, with gusts as high as 21 mph.

    High: 60 °F

    Sunny

  • Monday Night

    Monday Night: Mostly cloudy, with a low around 42. North northeast wind around 5 mph becoming calm in the evening.

    Low: 42 °F

    Mostly Cloudy

  • Tuesday

    Tuesday: Partly sunny, with a high near 62. Calm wind becoming southeast around 5 mph.

    High: 62 °F

    Partly Sunny

  • Tuesday Night

    Tuesday Night: A slight chance of showers. Mostly cloudy, with a low around 46. Calm wind.

    Low: 46 °F

    Slight Chance
    Showers

  • Wednesday

    Wednesday: A slight chance of showers before 1pm. Partly sunny, with a high near 71. Calm wind becoming south 5 to 7 mph in the morning.

    High: 71 °F

    Slight Chance
    Showers

Detailed Forecast

Today
Sunny, with a high near 85. Calm wind becoming west southwest 5 to 7 mph in the morning.
Tonight
Clear, with a low around 61. South southwest wind 5 to 8 mph.
Sunday
Sunny, with a high near 85. South southwest wind 8 to 15 mph, with gusts as high as 26 mph.
Sunday Night
A 30 percent chance of showers and thunderstorms before 1am. Mostly cloudy, then gradually becoming mostly clear, with a low around 40. Southwest wind 7 to 16 mph becoming north in the evening. Winds could gust as high as 26 mph.
Monday
Sunny, with a high near 60. North northeast wind around 9 mph, with gusts as high as 21 mph.
Monday Night
Mostly cloudy, with a low around 42. North northeast wind around 5 mph becoming calm in the evening.
Tuesday
Partly sunny, with a high near 62. Calm wind becoming southeast around 5 mph.
Tuesday Night
A slight chance of showers. Mostly cloudy, with a low around 46. Calm wind.
Wednesday
A slight chance of showers before 1pm. Partly sunny, with a high near 71. Calm wind becoming south 5 to 7 mph in the morning.
Wednesday Night
A slight chance of showers. Partly cloudy, with a low around 56. South wind 3 to 5 mph.
Thursday
A slight chance of showers and thunderstorms. Sunny, with a high near 81. South southwest wind 6 to 10 mph, with gusts as high as 20 mph.
Thursday Night
A chance of showers and thunderstorms. Partly cloudy, with a low around 52. Southwest wind around 8 mph becoming north after midnight.
Friday
A chance of showers. Partly sunny, with a high near 64. North northeast wind around 9 mph, with gusts as high as 20 mph.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Simpson IL
 37.46°N 88.77°W
Last Update:
6:36 am CDT Mar 21, 2026
Forecast Valid:
6am CDT Mar 21, 2026-6pm CDT Mar 27, 2026
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation