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

Areas of Dangerous Heat and Heavy Rain with Possible Flooding into this Weekend

Hot temperatures and high humidity are forecast to continue across the mid-Mississippi Valley into this weekend with heat advisories in effect. Heavy to excessive rainfall occurring at times through Sunday could bring areas of flooding to parts of the upper Midwest, central Great Lakes, southern New England and Virginia/North Carolina tidewater region. Read More >

Hazardous Weather Conditions

Current conditions at

St. Louis Regional Airport (KALN)

Lat: 38.89°NLon: 90.03°WElev: 518ft.

Fair

81°F

27°C

Humidity 79%
Wind Speed Calm
Barometer 30.15 in
Dewpoint 73°F (23°C)
Visibility 10.00 mi
Heat Index86°F (30°C)
Last update 17 Sep 8:45 pm CDT
Extended Forecast for

Mount Olive IL

Heat Advisory September 17, 09:34pm until September 18, 08:00pm
Click here for hazard details and duration
Heat Advisory
  •  
    Heat Advisory September 17, 09:34pm until September 18, 08:00pm

    NOW until 8:00pm Fri

    Heat Advisory

  • Tonight

    Low: 70 °F

    Mostly Clear

  • Friday

    Friday: A slight chance of showers and thunderstorms between 1pm and 2pm. Mostly cloudy, then gradual clearing during the afternoon, with a high near 93. Heat index values as high as 101. Northeast wind 3 to 7 mph. Chance of precipitation is 20%.

    High: 93 °F

    Mostly Sunny
    then Slight
    Chance
    T-storms

  • Friday Night

    Friday Night: Mostly clear, with a low around 70. Southeast wind around 8 mph.

    Low: 70 °F

    Mostly Clear

  • Saturday

    Saturday: Mostly sunny, with a high near 95. South wind 5 to 8 mph becoming west in the morning.

    High: 95 °F

    Mostly Sunny

  • Saturday Night

    Saturday Night: Partly cloudy, with a low around 70. Light south wind.

    Low: 70 °F

    Partly Cloudy

  • Sunday

    Sunday: A slight chance of showers, with thunderstorms also possible after 1pm. Mostly sunny, with a high near 91. Chance of precipitation is 20%.

    High: 91 °F

    Slight Chance
    Showers then
    Slight Chance
    T-storms

  • Sunday Night

    Sunday Night: A 40 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 65.

    Low: 65 °F

    Chance
    T-storms

  • Monday

    Monday: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 81.

    High: 81 °F

    Chance
    Showers then
    Chance
    T-storms

Detailed Forecast

Tonight
Mostly clear, with a low around 70. Light and variable wind becoming southwest around 5 mph after midnight.
Friday
A slight chance of showers and thunderstorms between 1pm and 2pm. Mostly cloudy, then gradual clearing during the afternoon, with a high near 93. Heat index values as high as 101. Northeast wind 3 to 7 mph. Chance of precipitation is 20%.
Friday Night
Mostly clear, with a low around 70. Southeast wind around 8 mph.
Saturday
Mostly sunny, with a high near 95. South wind 5 to 8 mph becoming west in the morning.
Saturday Night
Partly cloudy, with a low around 70. Light south wind.
Sunday
A slight chance of showers, with thunderstorms also possible after 1pm. Mostly sunny, with a high near 91. Chance of precipitation is 20%.
Sunday Night
A 40 percent chance of showers and thunderstorms, mainly after 1am. Mostly cloudy, with a low around 65.
Monday
A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 81.
Monday Night
A 20 percent chance of showers and thunderstorms before 1am. Mostly cloudy, with a low around 59.
Tuesday
Partly sunny, with a high near 74.
Tuesday Night
Partly cloudy, with a low around 55.
Wednesday
Mostly sunny, with a high near 76.
Wednesday Night
Partly cloudy, with a low around 56.
Thursday
Mostly sunny, with a high near 79.
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Forecast Area
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ABOUT THIS FORECAST

 
Point Forecast:
Mount Olive IL
 39.07°N 89.73°W (Elev. 669 ft)
Last Update:
6:06 pm CDT Sep 17, 2026
Forecast Valid:
9pm CDT Sep 17, 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