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

25°F

-4°C

Humidity 81%
Wind Speed Calm
Barometer 30.51 in (1033.5 mb)
Dewpoint 20°F (-7°C)
Visibility 10.00 mi
Last update 11 Jan 8:52 pm CST
Extended Forecast for

Saint Johns IL

  • Tonight

    Tonight: Clear, with a low around 24. Calm wind becoming south southwest 5 to 7 mph after midnight.

    Low: 24 °F

    Clear

  • Monday

    Monday: Sunny, with a high near 51. South southwest wind 7 to 10 mph.

    High: 51 °F

    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 35. South southwest wind 6 to 8 mph.

    Low: 35 °F

    Mostly Clear

  • Tuesday

    Tuesday: Mostly sunny, with a high near 59. Southwest wind 9 to 14 mph, with gusts as high as 21 mph.

    High: 59 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: A 20 percent chance of showers. Mostly cloudy, with a low around 40. Southwest wind 7 to 10 mph becoming west northwest after midnight.

    Low: 40 °F

    Slight Chance
    Showers

  • Wednesday

    Wednesday: A 20 percent chance of showers. Mostly cloudy, with a high near 45. Breezy, with a northwest wind 10 to 20 mph, with gusts as high as 29 mph.

    High: 45 °F

    Slight Chance
    Showers and
    Breezy

  • Wednesday Night

    Wednesday Night: Mostly cloudy, with a low around 19. Blustery, with a north northwest wind 14 to 20 mph, with gusts as high as 29 mph.

    Low: 19 °F

    Mostly Cloudy
    and Blustery
    then Partly
    Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 33. North northwest wind 6 to 13 mph, with gusts as high as 22 mph.

    High: 33 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Mostly cloudy, with a low around 26. South southwest wind 5 to 9 mph.

    Low: 26 °F

    Mostly Cloudy

Detailed Forecast

Tonight
Clear, with a low around 24. Calm wind becoming south southwest 5 to 7 mph after midnight.
Monday
Sunny, with a high near 51. South southwest wind 7 to 10 mph.
Monday Night
Mostly clear, with a low around 35. South southwest wind 6 to 8 mph.
Tuesday
Mostly sunny, with a high near 59. Southwest wind 9 to 14 mph, with gusts as high as 21 mph.
Tuesday Night
A 20 percent chance of showers. Mostly cloudy, with a low around 40. Southwest wind 7 to 10 mph becoming west northwest after midnight.
Wednesday
A 20 percent chance of showers. Mostly cloudy, with a high near 45. Breezy, with a northwest wind 10 to 20 mph, with gusts as high as 29 mph.
Wednesday Night
Mostly cloudy, with a low around 19. Blustery, with a north northwest wind 14 to 20 mph, with gusts as high as 29 mph.
Thursday
Mostly sunny, with a high near 33. North northwest wind 6 to 13 mph, with gusts as high as 22 mph.
Thursday Night
Mostly cloudy, with a low around 26. South southwest wind 5 to 9 mph.
Friday
Partly sunny, with a high near 43. Southwest wind 9 to 14 mph, with gusts as high as 21 mph.
Friday Night
Mostly cloudy, with a low around 24. West wind 6 to 9 mph.
Saturday
Partly sunny, with a high near 33. West northwest wind 9 to 13 mph, with gusts as high as 20 mph.
Saturday Night
Partly cloudy, with a low around 18. West wind 6 to 8 mph.
Sunday
Sunny, with a high near 32. West wind 8 to 13 mph, with gusts as high as 18 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:
6:12 pm CST Jan 11, 2026
Forecast Valid:
9pm CST Jan 11, 2026-6pm CST Jan 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