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.

Fair

91°F

33°C

Humidity 52%
Wind Speed W 8 G 16 mph
Barometer 30.09 in
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Heat Index98°F (37°C)
Last update 1 Sep 10:52 am CDT
Extended Forecast for

Saint Johns IL

Extreme Heat Warning until September 5, 08:00pm
Click here for hazard details and duration
Extreme Heat Warning
  •  
    Extreme Heat Warning until September 5, 08:00pm

    NOW until 8:00pm Sat

    Extreme Heat Warning

  • This Afternoon

    High: 100 °F

    Hot

  • Tonight

    Tonight: Clear, with a low around 76. Light south wind.

    Low: 76 °F

    Clear

  • Wednesday

    Wednesday: Sunny and hot, with a high near 101. Heat index values as high as 107. Calm wind becoming south southwest 5 to 8 mph in the morning.

    High: 101 °F

    Hot

  • Wednesday Night

    Wednesday Night: Clear, with a low around 76. South wind around 5 mph becoming calm in the evening.

    Low: 76 °F

    Clear

  • Thursday

    Thursday: Sunny and hot, with a high near 100. Calm wind becoming southwest 5 to 7 mph in the afternoon.

    High: 100 °F

    Hot

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 76. Light south wind.

    Low: 76 °F

    Mostly Clear

  • Friday

    Friday: Sunny and hot, with a high near 101. Light west southwest wind.

    High: 101 °F

    Hot

  • Friday Night

    Friday Night: Mostly clear, with a low around 76. Calm wind.

    Low: 76 °F

    Mostly Clear

Detailed Forecast

This Afternoon
Sunny and hot, with a high near 100. Heat index values as high as 106. South southwest wind 3 to 6 mph.
Tonight
Clear, with a low around 76. Light south wind.
Wednesday
Sunny and hot, with a high near 101. Heat index values as high as 107. Calm wind becoming south southwest 5 to 8 mph in the morning.
Wednesday Night
Clear, with a low around 76. South wind around 5 mph becoming calm in the evening.
Thursday
Sunny and hot, with a high near 100. Calm wind becoming southwest 5 to 7 mph in the afternoon.
Thursday Night
Mostly clear, with a low around 76. Light south wind.
Friday
Sunny and hot, with a high near 101. Light west southwest wind.
Friday Night
Mostly clear, with a low around 76. Calm wind.
Saturday
A slight chance of showers and thunderstorms. Sunny and hot, with a high near 100. Light and variable wind.
Saturday Night
Partly cloudy, with a low around 73. Calm wind.
Sunday
A slight chance of showers and thunderstorms. Mostly sunny, with a high near 96. Calm wind becoming north 5 to 7 mph in the afternoon.
Sunday Night
Mostly clear, with a low around 70. Light east wind.
Labor Day
Sunny, with a high near 94. Calm wind becoming east southeast around 6 mph in the afternoon.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Saint Johns IL
 38.03°N 89.24°W
Last Update:
11:51 am CDT Sep 1, 2026
Forecast Valid:
12pm CDT Sep 1, 2026-6pm CDT Sep 7, 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