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

74°F

23°C

Humidity 67%
Wind Speed S 13 mph
Barometer 29.94 in (1013.5 mb)
Dewpoint 62°F (17°C)
Visibility 10.00 mi
Last update 14 Apr 10:52 pm CDT
Extended Forecast for

Saint Johns IL

  • Tonight

    Tonight: Mostly cloudy, with a low around 69. South southwest wind 10 to 13 mph, with gusts as high as 22 mph.

    Low: 69 °F

    Mostly Cloudy

  • Wednesday

    Wednesday: A 30 percent chance of showers and thunderstorms, mainly between 2pm and 4pm. Partly sunny, with a high near 83. South southwest wind 10 to 16 mph, with gusts as high as 25 mph.

    High: 83 °F

    Slight Chance
    Showers then
    Chance
    T-storms

  • Wednesday Night

    Wednesday Night: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 64. South southwest wind 9 to 11 mph, with gusts as high as 20 mph. Chance of precipitation is 70%.

    Low: 64 °F

    Chance
    T-storms then
    Showers
    Likely

  • Thursday

    Thursday: Showers and possibly a thunderstorm before 10am, then showers between 10am and 1pm, then showers likely and possibly a thunderstorm after 1pm. High near 81. Southwest wind 9 to 13 mph, with gusts as high as 18 mph. Chance of precipitation is 80%.

    High: 81 °F

    Showers

  • Thursday Night

    Thursday Night: A chance of thunderstorms before 7pm. Mostly clear, with a low around 61. South southwest wind 3 to 7 mph. Chance of precipitation is 30%.

    Low: 61 °F

    Chance
    T-storms then
    Mostly Clear

  • Friday

    Friday: A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 86. South wind 5 to 11 mph, with gusts as high as 20 mph.

    High: 86 °F

    Mostly Sunny
    then Chance
    T-storms

  • Friday Night

    Friday Night: A 50 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 61. South wind around 11 mph, with gusts as high as 21 mph.

    Low: 61 °F

    Slight Chance
    T-storms then
    Chance
    Showers

  • Saturday

    Saturday: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 75. South southwest wind 13 to 16 mph becoming west in the afternoon. Winds could gust as high as 24 mph.

    High: 75 °F

    Chance
    T-storms then
    Showers
    Likely

  • Saturday Night

    Saturday Night: A chance of showers before 1am. Partly cloudy, with a low around 42. West northwest wind 9 to 11 mph, with gusts as high as 20 mph.

    Low: 42 °F

    Chance
    Showers

Detailed Forecast

Tonight
Mostly cloudy, with a low around 69. South southwest wind 10 to 13 mph, with gusts as high as 22 mph.
Wednesday
A 30 percent chance of showers and thunderstorms, mainly between 2pm and 4pm. Partly sunny, with a high near 83. South southwest wind 10 to 16 mph, with gusts as high as 25 mph.
Wednesday Night
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 64. South southwest wind 9 to 11 mph, with gusts as high as 20 mph. Chance of precipitation is 70%.
Thursday
Showers and possibly a thunderstorm before 10am, then showers between 10am and 1pm, then showers likely and possibly a thunderstorm after 1pm. High near 81. Southwest wind 9 to 13 mph, with gusts as high as 18 mph. Chance of precipitation is 80%.
Thursday Night
A chance of thunderstorms before 7pm. Mostly clear, with a low around 61. South southwest wind 3 to 7 mph. Chance of precipitation is 30%.
Friday
A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 86. South wind 5 to 11 mph, with gusts as high as 20 mph.
Friday Night
A 50 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 61. South wind around 11 mph, with gusts as high as 21 mph.
Saturday
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 75. South southwest wind 13 to 16 mph becoming west in the afternoon. Winds could gust as high as 24 mph.
Saturday Night
A chance of showers before 1am. Partly cloudy, with a low around 42. West northwest wind 9 to 11 mph, with gusts as high as 20 mph.
Sunday
Sunny, with a high near 63. West northwest wind 8 to 13 mph, with gusts as high as 20 mph.
Sunday Night
Clear, with a low around 40. North northwest wind 3 to 7 mph.
Monday
Sunny, with a high near 68. Southeast wind 5 to 7 mph.
Monday Night
Mostly clear, with a low around 46. South southeast wind around 6 mph.
Tuesday
Sunny, with a high near 72. South wind 6 to 11 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:
9:42 pm CDT Apr 14, 2026
Forecast Valid:
11pm CDT Apr 14, 2026-6pm CDT Apr 21, 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