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.

Partly Cloudy

82°F

28°C

Humidity 41%
Wind Speed Vrbl 5 mph
Barometer 30.02 in (1016.1 mb)
Dewpoint 56°F (13°C)
Visibility 10.00 mi
Heat Index82°F (28°C)
Last update 19 Jun 12:52 pm CDT
Extended Forecast for

Saint Johns IL

  • Juneteenth

    Juneteenth: Mostly sunny, with a high near 84. Calm wind.

    High: 84 °F

    Mostly Sunny

  • Tonight

    Tonight: Mostly cloudy, with a low around 63. Calm wind.

    Low: 63 °F

    Mostly Cloudy

  • Saturday

    Saturday: Mostly sunny, with a high near 87. Light southwest wind.

    High: 87 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 67. Calm wind.

    Low: 67 °F

    Partly Cloudy

  • Sunday

    Sunday: A chance of showers and thunderstorms, then showers and possibly a thunderstorm after 7am. High near 85. Light and variable wind becoming south southwest 11 to 16 mph in the morning. Winds could gust as high as 24 mph. Chance of precipitation is 80%.

    High: 85 °F

    Showers

  • Sunday Night

    Sunday Night: Showers and possibly a thunderstorm. Low around 68. West wind 10 to 16 mph, with gusts as high as 23 mph. Chance of precipitation is 100%.

    Low: 68 °F

    Showers

  • Monday

    Monday: A 40 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 81. Northwest wind 8 to 11 mph.

    High: 81 °F

    Chance
    T-storms then
    Chance
    Showers

  • Monday Night

    Monday Night: Partly cloudy, with a low around 62. North wind 5 to 9 mph becoming calm in the evening.

    Low: 62 °F

    Partly Cloudy

  • Tuesday

    Tuesday: Mostly sunny, with a high near 81. Light north northeast wind.

    High: 81 °F

    Mostly Sunny

Detailed Forecast

Juneteenth
Mostly sunny, with a high near 84. Calm wind.
Tonight
Mostly cloudy, with a low around 63. Calm wind.
Saturday
Mostly sunny, with a high near 87. Light southwest wind.
Saturday Night
Partly cloudy, with a low around 67. Calm wind.
Sunday
A chance of showers and thunderstorms, then showers and possibly a thunderstorm after 7am. High near 85. Light and variable wind becoming south southwest 11 to 16 mph in the morning. Winds could gust as high as 24 mph. Chance of precipitation is 80%.
Sunday Night
Showers and possibly a thunderstorm. Low around 68. West wind 10 to 16 mph, with gusts as high as 23 mph. Chance of precipitation is 100%.
Monday
A 40 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 81. Northwest wind 8 to 11 mph.
Monday Night
Partly cloudy, with a low around 62. North wind 5 to 9 mph becoming calm in the evening.
Tuesday
Mostly sunny, with a high near 81. Light north northeast wind.
Tuesday Night
Partly cloudy, with a low around 62. Calm wind.
Wednesday
Mostly sunny, with a high near 83. Calm wind becoming west northwest around 5 mph in the afternoon.
Wednesday Night
Mostly clear, with a low around 62. Light west northwest wind.
Thursday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 83. Calm wind becoming west around 6 mph in the afternoon.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Saint Johns IL
 38.06°N 89.24°W
Last Update:
12:41 pm CDT Jun 19, 2026
Forecast Valid:
1pm CDT Jun 19, 2026-6pm CDT Jun 25, 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