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

54°F

12°C

Humidity 37%
Wind Speed NE 16 G 22 mph
Barometer 30.35 in (1028.0 mb)
Dewpoint 28°F (-2°C)
Visibility 10.00 mi
Wind Chill50°F (10°C)
Last update 23 Mar 3:52 pm CDT
Extended Forecast for

Saint Johns IL

  • This Afternoon

    This Afternoon: Partly sunny, with a steady temperature around 52. Light north northeast wind.

    High: 52 °F

    Partly Sunny

  • Tonight

    Tonight: Mostly cloudy, with a low around 36. East northeast wind around 7 mph.

    Low: 36 °F

    Mostly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 62. East wind around 6 mph.

    High: 62 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Partly cloudy, with a low around 43. East southeast wind 3 to 6 mph.

    Low: 43 °F

    Partly Cloudy

  • Wednesday

    Wednesday: Mostly sunny, with a high near 73. Light south southeast wind becoming south southwest 5 to 10 mph in the morning.

    High: 73 °F

    Mostly Sunny

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 61. South wind 8 to 10 mph, with gusts as high as 20 mph.

    Low: 61 °F

    Partly Cloudy

  • Thursday

    Thursday: Sunny, with a high near 85. South southwest wind 10 to 15 mph, with gusts as high as 23 mph.

    High: 85 °F

    Sunny

  • Thursday Night

    Thursday Night: A slight chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 43. South southwest wind 15 to 17 mph becoming north after midnight. Winds could gust as high as 26 mph.

    Low: 43 °F

    Slight Chance
    T-storms then
    Showers
    Likely

  • Friday

    Friday: Showers likely, mainly before 1pm. Mostly cloudy, with a high near 52. North wind around 17 mph, with gusts as high as 25 mph.

    High: 52 °F

    Showers
    Likely

Detailed Forecast

This Afternoon
Partly sunny, with a steady temperature around 52. Light north northeast wind.
Tonight
Mostly cloudy, with a low around 36. East northeast wind around 7 mph.
Tuesday
Mostly sunny, with a high near 62. East wind around 6 mph.
Tuesday Night
Partly cloudy, with a low around 43. East southeast wind 3 to 6 mph.
Wednesday
Mostly sunny, with a high near 73. Light south southeast wind becoming south southwest 5 to 10 mph in the morning.
Wednesday Night
Partly cloudy, with a low around 61. South wind 8 to 10 mph, with gusts as high as 20 mph.
Thursday
Sunny, with a high near 85. South southwest wind 10 to 15 mph, with gusts as high as 23 mph.
Thursday Night
A slight chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 43. South southwest wind 15 to 17 mph becoming north after midnight. Winds could gust as high as 26 mph.
Friday
Showers likely, mainly before 1pm. Mostly cloudy, with a high near 52. North wind around 17 mph, with gusts as high as 25 mph.
Friday Night
Partly cloudy, with a low around 32. North wind 9 to 15 mph, with gusts as high as 22 mph.
Saturday
Sunny, with a high near 56. East northeast wind around 7 mph.
Saturday Night
Partly cloudy, with a low around 37. Light southeast wind.
Sunday
Mostly sunny, with a high near 64. South wind 5 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:
4:11 pm CDT Mar 23, 2026
Forecast Valid:
4pm CDT Mar 23, 2026-6pm CDT Mar 29, 2026
 
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Additional Resources

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation