National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Hazardous Weather Conditions

Current conditions at

Southern Illinois Airport (KMDH)

Lat: 37.78°NLon: 89.25°WElev: 400ft.

Mostly Cloudy

56°F

13°C

Humidity 60%
Wind Speed S 6 mph
Barometer 29.96 in (1014.3 mb)
Dewpoint 42°F (6°C)
Visibility 10.00 mi
Last update 15 May 5:52 am CDT
Extended Forecast for

Saint Johns IL

  • Today

    Today: A slight chance of showers and thunderstorms between 8am and 10am. Partly sunny, with a high near 83. South southeast wind 7 to 15 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

    High: 83 °F

    Slight Chance
    T-storms then
    Mostly Sunny

  • Tonight

    Tonight: A slight chance of showers and thunderstorms before 1am, then a slight chance of showers between 1am and 4am, then a slight chance of showers and thunderstorms after 4am. Mostly cloudy, with a low around 67. South wind 8 to 11 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.

    Low: 67 °F

    Slight Chance
    T-storms

  • Saturday

    Saturday: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 85. South southwest wind around 11 mph, with gusts as high as 20 mph.

    High: 85 °F

    Chance
    T-storms

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 66. South wind around 9 mph.

    Low: 66 °F

    Partly Cloudy

  • Sunday

    Sunday: Sunny, with a high near 89. South wind 9 to 16 mph, with gusts as high as 23 mph.

    High: 89 °F

    Sunny

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 69. South wind 11 to 14 mph, with gusts as high as 22 mph.

    Low: 69 °F

    Mostly Clear

  • Monday

    Monday: A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 90. South wind 11 to 18 mph, with gusts as high as 26 mph.

    High: 90 °F

    Mostly Sunny
    then Chance
    T-storms

  • Monday Night

    Monday Night: A chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 71. South wind 13 to 16 mph, with gusts as high as 24 mph.

    Low: 71 °F

    Chance
    T-storms

  • Tuesday

    Tuesday: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 86. South southwest wind 13 to 17 mph, with gusts as high as 25 mph.

    High: 86 °F

    Chance
    T-storms then
    Showers
    Likely

Detailed Forecast

Today
A slight chance of showers and thunderstorms between 8am and 10am. Partly sunny, with a high near 83. South southeast wind 7 to 15 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.
Tonight
A slight chance of showers and thunderstorms before 1am, then a slight chance of showers between 1am and 4am, then a slight chance of showers and thunderstorms after 4am. Mostly cloudy, with a low around 67. South wind 8 to 11 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.
Saturday
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 85. South southwest wind around 11 mph, with gusts as high as 20 mph.
Saturday Night
Partly cloudy, with a low around 66. South wind around 9 mph.
Sunday
Sunny, with a high near 89. South wind 9 to 16 mph, with gusts as high as 23 mph.
Sunday Night
Mostly clear, with a low around 69. South wind 11 to 14 mph, with gusts as high as 22 mph.
Monday
A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 90. South wind 11 to 18 mph, with gusts as high as 26 mph.
Monday Night
A chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 71. South wind 13 to 16 mph, with gusts as high as 24 mph.
Tuesday
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Partly sunny, with a high near 86. South southwest wind 13 to 17 mph, with gusts as high as 25 mph.
Tuesday Night
Showers likely and possibly a thunderstorm before 1am, then a chance of showers. Mostly cloudy, with a low around 63. South southwest wind 6 to 14 mph becoming west northwest after midnight. Winds could gust as high as 20 mph.
Wednesday
A chance of showers and thunderstorms. Partly sunny, with a high near 78. North wind 7 to 9 mph.
Wednesday Night
A chance of showers and thunderstorms. Mostly cloudy, with a low around 57. North northeast wind 5 to 8 mph.
Thursday
A chance of showers and thunderstorms. Partly sunny, with a high near 77. Northeast wind around 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:
3:32 am CDT May 15, 2026
Forecast Valid:
6am CDT May 15, 2026-6pm CDT May 21, 2026
 
Forecast Discussion
 
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Additional Resources

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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