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 >

Current conditions at

St. Louis Downtown Airport (KCPS)

Lat: 38.56°NLon: 90.15°WElev: 410ft.

Fair

95°F

35°C

Humidity 51%
Wind Speed E 5 mph
Barometer 30.08 in (1018.1 mb)
Dewpoint 74°F (23°C)
Visibility 10.00 mi
Heat Index106°F (41°C)
Last update 18 Sep 1:53 pm CDT
Extended Forecast for

Swansea IL

Heat Advisory September 18, 02:24pm until September 19, 08:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory September 18, 02:24pm until September 19, 08:00pm

    NOW until 8:00pm Sat

    Heat Advisory

  • This Afternoon

    High: 98 °F

    Chance
    T-storms

  • Tonight

    Tonight: A 20 percent chance of showers and thunderstorms before 10pm.  Mostly clear, with a low around 73. Light and variable wind becoming southeast around 5 mph.

    Low: 73 °F

    Slight Chance
    T-storms then
    Mostly Clear

  • Saturday

    Saturday: Increasing clouds and hot, with a high near 98. Heat index values as high as 101. Light and variable wind becoming west 5 to 8 mph in the morning.

    High: 98 °F

    Hot

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 74. South wind 3 to 5 mph.

    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.  Mostly sunny, with a high near 94. West wind 3 to 7 mph.  Chance of precipitation is 20%.

    High: 94 °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 68.

    Low: 68 °F

    Chance
    Showers

  • Monday

    Monday: Showers likely, with thunderstorms also possible after 1pm.  Mostly cloudy, with a high near 82. Chance of precipitation is 70%.

    High: 82 °F

    Showers
    Likely

  • Monday Night

    Monday Night: A slight chance of showers and thunderstorms, then a chance of showers after 1am.  Mostly cloudy, with a low around 62. Chance of precipitation is 30%.

    Low: 62 °F

    Slight Chance
    T-storms then
    Chance
    Showers

Detailed Forecast

This Afternoon
A 30 percent chance of showers and thunderstorms, mainly after 5pm. Sunny and hot, with a high near 98. Heat index values as high as 107. Light southwest wind.
Tonight
A 20 percent chance of showers and thunderstorms before 10pm. Mostly clear, with a low around 73. Light and variable wind becoming southeast around 5 mph.
Saturday
Increasing clouds and hot, with a high near 98. Heat index values as high as 101. Light and variable wind becoming west 5 to 8 mph in the morning.
Saturday Night
Partly cloudy, with a low around 74. South wind 3 to 5 mph.
Sunday
A slight chance of showers between 1pm and 4pm, then a slight chance of showers and thunderstorms after 4pm. Mostly sunny, with a high near 94. 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 68.
Monday
Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 82. Chance of precipitation is 70%.
Monday Night
A slight chance of showers and thunderstorms, then a chance of showers after 1am. Mostly cloudy, with a low around 62. Chance of precipitation is 30%.
Tuesday
Mostly cloudy, with a high near 72.
Tuesday Night
Mostly cloudy, with a low around 55.
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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ABOUT THIS FORECAST

 
Point Forecast:
Swansea IL
 38.55°N 89.98°W (Elev. 551 ft)
2:01 pm CDT Sep 18, 2026
2pm CDT Sep 18, 2026-6pm CDT Sep 24, 2026
 
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Additional Resources

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