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

Dangerous Heat and Heavy Rainfall into the Weekend

Hot temperatures and high humidity are forecast to continue across the mid-Mississippi Valley into this weekend. Heat Advisories remain in effect. Heavy to excessive rainfall occurring at times through the weekend could bring areas of flooding to parts of the northern Rockies, upper Midwest, central Great Lakes, and southern New England. Read More >

Hazardous Weather Conditions

Current conditions at

St. Louis Downtown Airport (KCPS)

Lat: 38.56°NLon: 90.15°WElev: 410ft.

Fair

81°F

27°C

Humidity 77%
Wind Speed Calm
Barometer 30.16 in (1020.7 mb)
Dewpoint 73°F (23°C)
Visibility 10.00 mi
Heat Index86°F (30°C)
Last update 18 Sep 8:53 am CDT
Extended Forecast for

Caseyville IL

Heat Advisory September 18, 09:28am until September 19, 08:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory September 18, 09:28am until September 19, 08:00pm

    NOW until 8:00pm Sat

    Heat Advisory

  • Today

    High: 95 °F

    Sunny then
    Slight Chance
    T-storms

  • Tonight

    Tonight: A 20 percent chance of showers and thunderstorms before 11pm. Partly cloudy, with a low around 73. Northeast wind 5 to 7 mph becoming southeast after midnight.

    Low: 73 °F

    Slight Chance
    T-storms then
    Partly Cloudy

  • Saturday

    Saturday: Increasing clouds, with a high near 96. Heat index values as high as 102. South wind 5 to 7 mph becoming west in the afternoon.

    High: 96 °F

    Increasing
    Clouds

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 74. Calm wind becoming south around 5 mph after midnight.

    Low: 74 °F

    Partly Cloudy

  • Sunday

    Sunday: A slight chance of showers between 1pm and 4pm, then a slight chance of showers and thunderstorms after 4pm. Partly sunny, with a high near 93. West wind 3 to 7 mph. Chance of precipitation is 20%.

    High: 93 °F

    Mostly Sunny
    then Slight
    Chance
    T-storms

  • Sunday Night

    Sunday Night: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 69.

    Low: 69 °F

    Chance
    T-storms

  • Monday

    Monday: Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 82. Chance of precipitation is 70%.

    High: 82 °F

    Showers
    Likely

  • Monday Night

    Monday Night: A 30 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 61.

    Low: 61 °F

    Chance
    Showers

Detailed Forecast

Today
A slight chance of showers between 2pm and 4pm, then a slight chance of showers and thunderstorms after 4pm. Sunny, with a high near 95. Heat index values as high as 107. Calm wind becoming northeast around 5 mph. Chance of precipitation is 20%.
Tonight
A 20 percent chance of showers and thunderstorms before 11pm. Partly cloudy, with a low around 73. Northeast wind 5 to 7 mph becoming southeast after midnight.
Saturday
Increasing clouds, with a high near 96. Heat index values as high as 102. South wind 5 to 7 mph becoming west in the afternoon.
Saturday Night
Partly cloudy, with a low around 74. Calm wind becoming south around 5 mph after midnight.
Sunday
A slight chance of showers between 1pm and 4pm, then a slight chance of showers and thunderstorms after 4pm. Partly sunny, with a high near 93. West wind 3 to 7 mph. Chance of precipitation is 20%.
Sunday Night
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 69.
Monday
Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 82. Chance of precipitation is 70%.
Monday Night
A 30 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 61.
Tuesday
Partly sunny, with a high near 73.
Tuesday Night
Mostly cloudy, with a low around 56.
Wednesday
Mostly sunny, with a high near 75.
Wednesday Night
Partly cloudy, with a low around 56.
Thursday
Mostly sunny, with a high near 77.
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Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Caseyville IL
 38.64°N 90.03°W (Elev. 446 ft)
Last Update:
8:51 am CDT Sep 18, 2026
Forecast Valid:
9am CDT Sep 18, 2026-6pm CDT Sep 24, 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