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

49°F

9°C

Humidity 61%
Wind Speed NE 7 mph
Barometer 30.26 in (1024.5 mb)
Dewpoint 36°F (2°C)
Visibility 10.00 mi
Wind Chill46°F (8°C)
Last update 20 Apr 2:52 am CDT
Extended Forecast for

Saint Johns IL

  • Overnight

    Overnight: Partly cloudy, with a low around 42. Light northeast wind.

    Low: 42 °F

    Partly Cloudy

  • Monday

    Monday: Sunny, with a high near 67. Light and variable wind becoming east around 6 mph.

    High: 67 °F

    Sunny

  • Monday Night

    Monday Night: Mostly clear, with a low around 49. South southeast wind 3 to 7 mph.

    Low: 49 °F

    Mostly Clear

  • Tuesday

    Tuesday: Mostly sunny, with a high near 77. Southwest wind 6 to 15 mph, with gusts as high as 23 mph.

    High: 77 °F

    Mostly Sunny

  • Tuesday Night

    Tuesday Night: Mostly clear, with a low around 54. South southwest wind 7 to 11 mph, with gusts as high as 20 mph.

    Low: 54 °F

    Mostly Clear

  • Wednesday

    Wednesday: Sunny, with a high near 77. Southwest wind 6 to 9 mph.

    High: 77 °F

    Sunny

  • Wednesday Night

    Wednesday Night: Clear, with a low around 56. South wind around 6 mph.

    Low: 56 °F

    Clear

  • Thursday

    Thursday: Mostly sunny, with a high near 80. South wind 7 to 16 mph, with gusts as high as 24 mph.

    High: 80 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: A chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 63. South wind 11 to 13 mph, with gusts as high as 22 mph.

    Low: 63 °F

    Mostly Cloudy
    then Chance
    T-storms

Detailed Forecast

Overnight
Partly cloudy, with a low around 42. Light northeast wind.
Monday
Sunny, with a high near 67. Light and variable wind becoming east around 6 mph.
Monday Night
Mostly clear, with a low around 49. South southeast wind 3 to 7 mph.
Tuesday
Mostly sunny, with a high near 77. Southwest wind 6 to 15 mph, with gusts as high as 23 mph.
Tuesday Night
Mostly clear, with a low around 54. South southwest wind 7 to 11 mph, with gusts as high as 20 mph.
Wednesday
Sunny, with a high near 77. Southwest wind 6 to 9 mph.
Wednesday Night
Clear, with a low around 56. South wind around 6 mph.
Thursday
Mostly sunny, with a high near 80. South wind 7 to 16 mph, with gusts as high as 24 mph.
Thursday Night
A chance of showers and thunderstorms after 1am. Mostly cloudy, with a low around 63. South wind 11 to 13 mph, with gusts as high as 22 mph.
Friday
Showers and possibly a thunderstorm. Mostly cloudy, with a high near 75. South wind 11 to 13 mph, with gusts as high as 21 mph.
Friday Night
Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 54. Southwest wind 6 to 8 mph becoming north northwest after midnight.
Saturday
A chance of showers and thunderstorms. Mostly sunny, with a high near 74. North wind 7 to 9 mph.
Saturday Night
A chance of showers and thunderstorms. Partly cloudy, with a low around 52. North northeast wind around 6 mph.
Sunday
A chance of showers and thunderstorms. Mostly sunny, with a high near 73. North northeast wind 6 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:
1:26 am CDT Apr 20, 2026
Forecast Valid:
3am CDT Apr 20, 2026-6pm CDT Apr 26, 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