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

St. Louis Regional Airport (KALN)

Lat: 38.89°NLon: 90.03°WElev: 518ft.

Fair

74°F

23°C

Humidity 94%
Wind Speed Calm
Barometer 29.97 in
Dewpoint 72°F (22°C)
Visibility 10.00 mi
Last update 9 Jul 12:55 am CDT
Extended Forecast for

Alton IL

  • Overnight

    Overnight: Mostly clear, with a low around 73. Light south wind.

    Low: 73 °F

    Mostly Clear

  • Thursday

    Thursday: A slight chance of showers, then a chance of showers and thunderstorms after 1pm. Partly sunny, with a high near 92. Heat index values as high as 100. Southwest wind 3 to 7 mph. Chance of precipitation is 50%.

    High: 92 °F

    Mostly Sunny
    then Chance
    T-storms

  • Thursday Night

    Thursday Night: A 40 percent chance of showers and thunderstorms, mainly after 3am. Mostly cloudy, with a low around 73. Southwest wind around 6 mph becoming light and variable in the evening.

    Low: 73 °F

    Chance
    T-storms

  • Friday

    Friday: A 30 percent chance of showers and thunderstorms, mainly after 5pm. Partly sunny, with a high near 88. West wind 3 to 6 mph.

    High: 88 °F

    Chance
    T-storms

  • Friday Night

    Friday Night: Showers and thunderstorms likely, mainly between 7pm and 1am, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 72. North wind around 6 mph becoming calm in the evening. Chance of precipitation is 70%.

    Low: 72 °F

    T-storms
    Likely

  • Saturday

    Saturday: A 50 percent chance of showers and thunderstorms. Partly sunny, with a high near 87.

    High: 87 °F

    Chance
    Showers then
    Chance
    T-storms

  • Saturday Night

    Saturday Night: A chance of showers and thunderstorms before 1am, then a slight chance of showers. Partly cloudy, with a low around 70. Chance of precipitation is 30%.

    Low: 70 °F

    Chance
    Showers

  • Sunday

    Sunday: A 20 percent chance of showers. Mostly sunny, with a high near 87.

    High: 87 °F

    Slight Chance
    Showers

  • Sunday Night

    Sunday Night: Mostly clear, with a low around 69.

    Low: 69 °F

    Mostly Clear

Detailed Forecast

Overnight
Mostly clear, with a low around 73. Light south wind.
Thursday
A slight chance of showers, then a chance of showers and thunderstorms after 1pm. Partly sunny, with a high near 92. Heat index values as high as 100. Southwest wind 3 to 7 mph. Chance of precipitation is 50%.
Thursday Night
A 40 percent chance of showers and thunderstorms, mainly after 3am. Mostly cloudy, with a low around 73. Southwest wind around 6 mph becoming light and variable in the evening.
Friday
A 30 percent chance of showers and thunderstorms, mainly after 5pm. Partly sunny, with a high near 88. West wind 3 to 6 mph.
Friday Night
Showers and thunderstorms likely, mainly between 7pm and 1am, then showers likely and possibly a thunderstorm after 1am. Mostly cloudy, with a low around 72. North wind around 6 mph becoming calm in the evening. Chance of precipitation is 70%.
Saturday
A 50 percent chance of showers and thunderstorms. Partly sunny, with a high near 87.
Saturday Night
A chance of showers and thunderstorms before 1am, then a slight chance of showers. Partly cloudy, with a low around 70. Chance of precipitation is 30%.
Sunday
A 20 percent chance of showers. Mostly sunny, with a high near 87.
Sunday Night
Mostly clear, with a low around 69.
Monday
Sunny, with a high near 88.
Monday Night
Mostly clear, with a low around 70.
Tuesday
Sunny, with a high near 91.
Tuesday Night
Mostly clear, with a low around 72.
Wednesday
Sunny, with a high near 92.
Basemap Options
Click map to change the forecast location
Loading map...
Forecast Area
Tiles ©ESRI

ABOUT THIS FORECAST

 
Point Forecast:
Alton IL
 38.91°N 90.19°W (Elev. 538 ft)
Last Update:
10:31 pm CDT Jul 8, 2026
Forecast Valid:
1am CDT Jul 9, 2026-6pm CDT Jul 15, 2026
 
Forecast Discussion
 
Get as KML Get as XML

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