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

69°F

21°C

Humidity 68%
Wind Speed S 3 mph
Barometer 29.99 in (1015.2 mb)
Dewpoint 58°F (14°C)
Visibility 10.00 mi
Last update 11 Oct 7:52 pm CDT
Extended Forecast for

Saint Johns IL

  • Tonight

    Tonight: Mostly clear, with a low around 61. Calm wind becoming southwest around 5 mph after midnight.

    Low: 61 °F

    Mostly Clear

  • Columbus Day

    Columbus Day: Partly sunny, then gradually becoming sunny, with a high near 92. Southwest wind 5 to 14 mph, with gusts as high as 18 mph.

    High: 92 °F

    Becoming
    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 66. Southwest wind around 8 mph.

    Low: 66 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 93. Southwest wind 7 to 11 mph.

    High: 93 °F

    Sunny

  • Tuesday Night

    Tuesday Night: A 30 percent chance of showers and thunderstorms after 1am. Mostly clear, with a low around 70. South southwest wind 5 to 7 mph.

    Low: 70 °F

    Mostly Clear
    then Chance
    Showers

  • Wednesday

    Wednesday: Showers and possibly a thunderstorm. High near 85. Southwest wind 3 to 6 mph. Chance of precipitation is 90%.

    High: 85 °F

    Showers

  • Wednesday Night

    Wednesday Night: Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 64. Light and variable wind. Chance of precipitation is 60%.

    Low: 64 °F

    Showers
    Likely

  • Thursday

    Thursday: Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 80. East northeast wind 5 to 10 mph becoming south in the afternoon.

    High: 80 °F

    Showers
    Likely

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 55. West wind 6 to 11 mph.

    Low: 55 °F

    Chance
    T-storms

Detailed Forecast

Tonight
Mostly clear, with a low around 61. Calm wind becoming southwest around 5 mph after midnight.
Columbus Day
Partly sunny, then gradually becoming sunny, with a high near 92. Southwest wind 5 to 14 mph, with gusts as high as 18 mph.
Monday Night
Mostly clear, with a low around 66. Southwest wind around 8 mph.
Tuesday
Sunny, with a high near 93. Southwest wind 7 to 11 mph.
Tuesday Night
A 30 percent chance of showers and thunderstorms after 1am. Mostly clear, with a low around 70. South southwest wind 5 to 7 mph.
Wednesday
Showers and possibly a thunderstorm. High near 85. Southwest wind 3 to 6 mph. Chance of precipitation is 90%.
Wednesday Night
Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 64. Light and variable wind. Chance of precipitation is 60%.
Thursday
Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 80. East northeast wind 5 to 10 mph becoming south in the afternoon.
Thursday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 55. West wind 6 to 11 mph.
Friday
Partly sunny, with a high near 68. Breezy, with a northwest wind 16 to 23 mph, with gusts as high as 28 mph.
Friday Night
Partly cloudy, with a low around 40. North northwest wind 9 to 18 mph, with gusts as high as 22 mph.
Saturday
Sunny, with a high near 60. North wind 10 to 13 mph.
Saturday Night
Clear, with a low around 35. Light and variable wind.
Sunday
Sunny, with a high near 68. Calm wind becoming south 5 to 7 mph in the morning.
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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:
2:01 pm CDT Oct 11, 2026
Forecast Valid:
8pm CDT Oct 11, 2026-6pm CDT Oct 18, 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