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.

Fair

58°F

14°C

Humidity 67%
Wind Speed S 12 mph
Barometer 30.01 in (1015.8 mb)
Dewpoint 47°F (8°C)
Visibility 10.00 mi
Last update 20 Mar 1:52 am CDT
Extended Forecast for

Saint Johns IL

  • Overnight

    Overnight: Mostly clear, with a low around 52. South southwest wind around 8 mph, with gusts as high as 18 mph.

    Low: 52 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 81. West southwest wind 8 to 10 mph, with gusts as high as 18 mph.

    High: 81 °F

    Sunny

  • Friday Night

    Friday Night: Partly cloudy, with a low around 51. West southwest wind around 6 mph becoming light and variable after midnight.

    Low: 51 °F

    Partly Cloudy

  • Saturday

    Saturday: Sunny, with a high near 79. Calm wind becoming east around 5 mph in the afternoon.

    High: 79 °F

    Sunny

  • Saturday Night

    Saturday Night: Clear, with a low around 60. South wind 3 to 8 mph.

    Low: 60 °F

    Clear

  • Sunday

    Sunday: Sunny, with a high near 84. South southwest wind 9 to 15 mph, with gusts as high as 23 mph.

    High: 84 °F

    Sunny

  • Sunday Night

    Sunday Night: A 20 percent chance of showers before 1am. Partly cloudy, with a low around 43. West wind around 15 mph becoming north after midnight. Winds could gust as high as 24 mph.

    Low: 43 °F

    Slight Chance
    Showers

  • Monday

    Monday: Mostly sunny, with a high near 59. North wind 9 to 11 mph, with gusts as high as 20 mph.

    High: 59 °F

    Mostly Sunny

  • Monday Night

    Monday Night: Partly cloudy, with a low around 39. East northeast wind around 6 mph.

    Low: 39 °F

    Partly Cloudy

Detailed Forecast

Overnight
Mostly clear, with a low around 52. South southwest wind around 8 mph, with gusts as high as 18 mph.
Friday
Sunny, with a high near 81. West southwest wind 8 to 10 mph, with gusts as high as 18 mph.
Friday Night
Partly cloudy, with a low around 51. West southwest wind around 6 mph becoming light and variable after midnight.
Saturday
Sunny, with a high near 79. Calm wind becoming east around 5 mph in the afternoon.
Saturday Night
Clear, with a low around 60. South wind 3 to 8 mph.
Sunday
Sunny, with a high near 84. South southwest wind 9 to 15 mph, with gusts as high as 23 mph.
Sunday Night
A 20 percent chance of showers before 1am. Partly cloudy, with a low around 43. West wind around 15 mph becoming north after midnight. Winds could gust as high as 24 mph.
Monday
Mostly sunny, with a high near 59. North wind 9 to 11 mph, with gusts as high as 20 mph.
Monday Night
Partly cloudy, with a low around 39. East northeast wind around 6 mph.
Tuesday
Partly sunny, with a high near 60. Southeast wind around 6 mph.
Tuesday Night
Mostly cloudy, with a low around 43. East wind 3 to 6 mph.
Wednesday
Partly sunny, with a high near 66. East wind 6 to 9 mph.
Wednesday Night
Partly cloudy, with a low around 50. Southeast wind 8 to 10 mph.
Thursday
A slight chance of showers. Sunny, with a high near 77. South southwest wind 10 to 14 mph, with gusts as high as 22 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:
1:26 am CDT Mar 20, 2026
Forecast Valid:
2am CDT Mar 20, 2026-6pm CDT Mar 26, 2026
 
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Additional Resources

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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