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

45°F

7°C

Humidity 52%
Wind Speed SW 12 mph
Barometer 30.20 in (1022.7 mb)
Dewpoint 28°F (-2°C)
Visibility 10.00 mi
Wind Chill39°F (4°C)
Last update 12 Jan 8:52 pm CST
Extended Forecast for

Saint Johns IL

  • Tonight

    Tonight: Mostly clear, with a low around 35. South southwest wind 7 to 10 mph.

    Low: 35 °F

    Mostly Clear

  • Tuesday

    Tuesday: Sunny, with a high near 60. Southwest wind 9 to 14 mph, with gusts as high as 21 mph.

    High: 60 °F

    Sunny

  • Tuesday Night

    Tuesday Night: A 40 percent chance of showers. Mostly cloudy, with a low around 39. West southwest wind around 7 mph becoming northwest after midnight.

    Low: 39 °F

    Chance
    Showers

  • Wednesday

    Wednesday: Mostly cloudy, with a high near 44. North northwest wind 8 to 18 mph, with gusts as high as 26 mph.

    High: 44 °F

    Mostly Cloudy

  • Wednesday Night

    Wednesday Night: Partly cloudy, with a low around 18. North northwest wind 10 to 18 mph, with gusts as high as 26 mph.

    Low: 18 °F

    Partly Cloudy

  • Thursday

    Thursday: Sunny, with a high near 31. Northwest wind 5 to 10 mph becoming southwest in the afternoon.

    High: 31 °F

    Sunny

  • Thursday Night

    Thursday Night: Mostly cloudy, with a low around 23. South southwest wind 5 to 11 mph, with gusts as high as 20 mph.

    Low: 23 °F

    Mostly Cloudy

  • Friday

    Friday: Partly sunny, with a high near 44. West southwest wind 11 to 15 mph, with gusts as high as 23 mph.

    High: 44 °F

    Partly Sunny

  • Friday Night

    Friday Night: Mostly cloudy, with a low around 20. West wind around 10 mph, with gusts as high as 18 mph.

    Low: 20 °F

    Mostly Cloudy

Detailed Forecast

Tonight
Mostly clear, with a low around 35. South southwest wind 7 to 10 mph.
Tuesday
Sunny, with a high near 60. Southwest wind 9 to 14 mph, with gusts as high as 21 mph.
Tuesday Night
A 40 percent chance of showers. Mostly cloudy, with a low around 39. West southwest wind around 7 mph becoming northwest after midnight.
Wednesday
Mostly cloudy, with a high near 44. North northwest wind 8 to 18 mph, with gusts as high as 26 mph.
Wednesday Night
Partly cloudy, with a low around 18. North northwest wind 10 to 18 mph, with gusts as high as 26 mph.
Thursday
Sunny, with a high near 31. Northwest wind 5 to 10 mph becoming southwest in the afternoon.
Thursday Night
Mostly cloudy, with a low around 23. South southwest wind 5 to 11 mph, with gusts as high as 20 mph.
Friday
Partly sunny, with a high near 44. West southwest wind 11 to 15 mph, with gusts as high as 23 mph.
Friday Night
Mostly cloudy, with a low around 20. West wind around 10 mph, with gusts as high as 18 mph.
Saturday
Partly sunny, with a high near 30. West wind 10 to 14 mph, with gusts as high as 21 mph.
Saturday Night
Partly cloudy, with a low around 12. West northwest wind around 10 mph.
Sunday
Mostly sunny, with a high near 26. West northwest wind 8 to 13 mph, with gusts as high as 18 mph.
Sunday Night
Mostly clear, with a low around 14. West southwest wind around 7 mph.
M.L.King Day
Mostly sunny, with a high near 36. West southwest wind 7 to 11 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:
6:32 pm CST Jan 12, 2026
Forecast Valid:
9pm CST Jan 12, 2026-6pm CST Jan 19, 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