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

Southern Illinois Airport (KMDH)

Lat: 37.78°NLon: 89.25°WElev: 400ft.

Overcast

37°F

3°C

Humidity 46%
Wind Speed S 13 mph
Barometer 30.10 in (1019.5 mb)
Dewpoint 18°F (-8°C)
Visibility 10.00 mi
Wind Chill29°F (-2°C)
Last update 18 Mar 4:52 am CDT
Extended Forecast for

Saint Johns IL

  • Overnight

    Overnight: A 20 percent chance of showers. Mostly cloudy, with a steady temperature around 35. South wind around 9 mph, with gusts as high as 21 mph.

    Low: 35 °F

    Slight Chance
    Showers

  • Wednesday

    Wednesday: Partly sunny, then gradually becoming sunny, with a high near 62. South wind 10 to 14 mph, with gusts as high as 23 mph.

    High: 62 °F

    Becoming
    Sunny

  • Wednesday Night

    Wednesday Night: Increasing clouds, with a low around 43. South wind around 6 mph.

    Low: 43 °F

    Increasing
    Clouds

  • Thursday

    Thursday: Mostly cloudy, then gradually becoming sunny, with a high near 72. South wind around 6 mph becoming west in the afternoon.

    High: 72 °F

    Decreasing
    Clouds

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 48. Light and variable wind.

    Low: 48 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 77. Southwest wind 3 to 8 mph.

    High: 77 °F

    Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 54. South southwest wind around 6 mph.

    Low: 54 °F

    Partly Cloudy

  • Saturday

    Saturday: Sunny, with a high near 78. West wind around 6 mph.

    High: 78 °F

    Sunny

  • Saturday Night

    Saturday Night: Clear, with a low around 56. South southwest wind 6 to 8 mph.

    Low: 56 °F

    Clear

Detailed Forecast

Overnight
A 20 percent chance of showers. Mostly cloudy, with a steady temperature around 35. South wind around 9 mph, with gusts as high as 21 mph.
Wednesday
Partly sunny, then gradually becoming sunny, with a high near 62. South wind 10 to 14 mph, with gusts as high as 23 mph.
Wednesday Night
Increasing clouds, with a low around 43. South wind around 6 mph.
Thursday
Mostly cloudy, then gradually becoming sunny, with a high near 72. South wind around 6 mph becoming west in the afternoon.
Thursday Night
Mostly clear, with a low around 48. Light and variable wind.
Friday
Sunny, with a high near 77. Southwest wind 3 to 8 mph.
Friday Night
Partly cloudy, with a low around 54. South southwest wind around 6 mph.
Saturday
Sunny, with a high near 78. West wind around 6 mph.
Saturday Night
Clear, with a low around 56. South southwest wind 6 to 8 mph.
Sunday
Sunny, with a high near 81. South southwest wind 9 to 14 mph, with gusts as high as 22 mph.
Sunday Night
Partly cloudy, with a low around 39. North northeast wind around 14 mph, with gusts as high as 22 mph.
Monday
Partly sunny, with a high near 55. Northeast wind 11 to 13 mph, with gusts as high as 20 mph.
Monday Night
Mostly cloudy, with a low around 36. Northeast wind 6 to 8 mph.
Tuesday
A slight chance of showers. Partly sunny, with a high near 60. East wind 6 to 8 mph.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Saint Johns IL
 38.03°N 89.24°W
Last Update:
4:21 am CDT Mar 18, 2026
Forecast Valid:
5am CDT Mar 18, 2026-6pm CDT Mar 24, 2026
 
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Additional Resources

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High Temperature

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Chance of Precipitation