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

St. Louis Regional Airport (KALN)

Lat: 38.89°NLon: 90.03°WElev: 518ft.

Fair

51°F

11°C

Humidity 92%
Wind Speed Calm
Barometer 30.04 in
Dewpoint 49°F (9°C)
Visibility 10.00 mi
Last update 29 Sep 1:15 am CDT
Extended Forecast for

Williamson IL

  • Overnight

    Overnight: Clear, with a low around 49. Calm wind.

    Low: 49 °F

    Clear

  • Tuesday

    Tuesday: Sunny, with a high near 83. South wind 3 to 8 mph.

    High: 83 °F

    Sunny

  • Tuesday Night

    Tuesday Night: Increasing clouds, with a low around 62. Southeast wind 3 to 6 mph.

    Low: 62 °F

    Increasing
    Clouds

  • Wednesday

    Wednesday: Partly sunny, with a high near 89. South wind 5 to 10 mph.

    High: 89 °F

    Partly Sunny

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 68. South wind 7 to 9 mph.

    Low: 68 °F

    Mostly Cloudy

  • Thursday

    Thursday: A 40 percent chance of showers after 1pm. Mostly cloudy, with a high near 88.

    High: 88 °F

    Mostly Cloudy
    then Chance
    Showers

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 64. Chance of precipitation is 70%.

    Low: 64 °F

    Showers
    Likely

  • Friday

    Friday: Showers likely, mainly before 1pm. Mostly cloudy, with a high near 74. Chance of precipitation is 70%.

    High: 74 °F

    Showers
    Likely

  • Friday Night

    Friday Night: A 30 percent chance of showers. Mostly cloudy, with a low around 56.

    Low: 56 °F

    Chance
    Showers

Detailed Forecast

Overnight
Clear, with a low around 49. Calm wind.
Tuesday
Sunny, with a high near 83. South wind 3 to 8 mph.
Tuesday Night
Increasing clouds, with a low around 62. Southeast wind 3 to 6 mph.
Wednesday
Partly sunny, with a high near 89. South wind 5 to 10 mph.
Wednesday Night
Mostly cloudy, with a low around 68. South wind 7 to 9 mph.
Thursday
A 40 percent chance of showers after 1pm. Mostly cloudy, with a high near 88.
Thursday Night
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 64. Chance of precipitation is 70%.
Friday
Showers likely, mainly before 1pm. Mostly cloudy, with a high near 74. Chance of precipitation is 70%.
Friday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 56.
Saturday
A 30 percent chance of showers, mainly before 1pm. Mostly cloudy, with a high near 70.
Saturday Night
A 30 percent chance of showers. Mostly cloudy, with a low around 56.
Sunday
Partly sunny, with a high near 71.
Sunday Night
Mostly clear, with a low around 50.
Monday
Sunny, with a high near 70.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Williamson IL
 38.98°N 89.76°W (Elev. 597 ft)
Last Update:
1:26 am CDT Sep 29, 2026
Forecast Valid:
1am CDT Sep 29, 2026-6pm CDT Oct 5, 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