Thunderstorms and Heavy Rain in the Mid-South; Heat Continues in the Southeast and Southwest

Severe thunderstorms and heavy rain are expected across portions of the mid-Mississippi Valley into the Ohio Valley and portions of Arizona. Dangerous heat persists in the South and Southeast while building into the Southwest. Overnight lows will be so warm that, when combined with oppressive dew points, little-to-no relief from the scorching daytime highs will be available. Read More >

Current conditions at

St. Louis Regional Airport (KALN)

Lat: 38.89°NLon: 90.03°WElev: 518ft.

Fair

73°F

23°C

Humidity 89%
Wind Speed SE 6 mph
Barometer 29.95 in
Dewpoint 70°F (21°C)
Visibility 10.00 mi
Last update 18 Aug 8:50 pm CDT
Extended Forecast for

2 Miles S Donnellson IL

  • Tonight

    Tonight: A 30 percent chance of showers and thunderstorms, mainly after 4am.  Increasing clouds, with a low around 67. Light and variable wind.

    Low: 67 °F

    Clear then
    Chance
    T-storms

  • Wednesday

    Wednesday: Showers and thunderstorms likely, mainly before 10am.  Mostly cloudy, with a high near 78. South wind around 6 mph.  Chance of precipitation is 70%.

    High: 78 °F

    T-storms
    Likely then
    Chance
    T-storms

  • Wednesday Night

    Wednesday Night: A 20 percent chance of showers and thunderstorms, mainly between 11pm and midnight.  Mostly cloudy, with a low around 64. North wind 3 to 6 mph.

    Low: 64 °F

    Slight Chance
    T-storms then
    Mostly Cloudy

  • Thursday

    Thursday: Mostly sunny, with a high near 81. Northeast wind 3 to 8 mph.

    High: 81 °F

    Mostly Sunny

  • Thursday Night

    Thursday Night: Mostly clear, with a low around 62. Calm wind.

    Low: 62 °F

    Mostly Clear

  • Friday

    Friday: Sunny, with a high near 83.

    High: 83 °F

    Sunny

  • Friday Night

    Friday Night: A 20 percent chance of showers and thunderstorms.  Mostly clear, with a low around 64.

    Low: 64 °F

    Slight Chance
    T-storms

  • Saturday

    Saturday: A 20 percent chance of showers and thunderstorms after 1pm.  Sunny, with a high near 83.

    High: 83 °F

    Sunny then
    Slight Chance
    T-storms

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 62.

    Low: 62 °F

    Mostly Clear

Detailed Forecast

Tonight
A 30 percent chance of showers and thunderstorms, mainly after 4am. Increasing clouds, with a low around 67. Light and variable wind.
Wednesday
Showers and thunderstorms likely, mainly before 10am. Mostly cloudy, with a high near 78. South wind around 6 mph. Chance of precipitation is 70%.
Wednesday Night
A 20 percent chance of showers and thunderstorms, mainly between 11pm and midnight. Mostly cloudy, with a low around 64. North wind 3 to 6 mph.
Thursday
Mostly sunny, with a high near 81. Northeast wind 3 to 8 mph.
Thursday Night
Mostly clear, with a low around 62. Calm wind.
Friday
Sunny, with a high near 83.
Friday Night
A 20 percent chance of showers and thunderstorms. Mostly clear, with a low around 64.
Saturday
A 20 percent chance of showers and thunderstorms after 1pm. Sunny, with a high near 83.
Saturday Night
Mostly clear, with a low around 62.
Sunday
Sunny, with a high near 80.
Sunday Night
A 20 percent chance of showers. Partly cloudy, with a low around 61.
Monday
A 20 percent chance of showers. Mostly sunny, with a high near 82.
Monday Night
A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 65.
Tuesday
Mostly sunny, with a high near 85.
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ABOUT THIS FORECAST

 
Point Forecast:
2 Miles S Donnellson IL
 39°N 89.47°W (Elev. 600 ft)
8:51 pm CDT Aug 18, 2026
9pm CDT Aug 18, 2026-6pm CDT Aug 25, 2026
 
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Additional Resources

Radar & Satellite Image

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Hourly Weather Forecast

National Digital Forecast Database