National Weather Service Forecast for: Arnold MO
Issued by: National Weather Service Saint Louis, MO
Updated: 2:21 pm CDT Jul 28, 2026
 
Tonight

Tonight: Cloudy during the early evening, then gradual clearing, with a low around 71. Northeast wind 3 to 5 mph.
Gradual
Clearing
 Wednesday

Wednesday: Sunny, with a high near 89. Calm wind becoming northeast around 6 mph in the afternoon.
Sunny
 Wednesday
Night
Wednesday Night: Clear, with a low around 66. East wind around 5 mph becoming calm in the evening.
Clear
 Thursday

Thursday: Sunny, with a high near 89. Light southeast wind.
Sunny
 Thursday
Night
Thursday Night: Partly cloudy, with a low around 68. East wind around 5 mph becoming calm in the evening.
Partly Cloudy
 Friday

Friday: Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 86. Chance of precipitation is 60%.
Showers
Likely
 Friday
Night
Friday Night: Showers likely and possibly a thunderstorm before 1am, then a chance of showers. Mostly cloudy, with a low around 69. Chance of precipitation is 60%.
Showers
Likely
 Saturday

Saturday: A chance of showers, with thunderstorms also possible after 1pm. Partly sunny, with a high near 80. Chance of precipitation is 50%.
Chance
Showers
 Saturday
Night
Saturday Night: A chance of showers and thunderstorms before 1am, then a slight chance of showers. Mostly cloudy, with a low around 68. Chance of precipitation is 30%.
Chance
Showers
Lo 71 °F Hi 89 °F Lo 66 °F Hi 89 °F Lo 68 °F Hi 86 °F Lo 69 °F Hi 80 °F Lo 68 °F

Extreme Heat Warning
 

Tonight
 
 Cloudy during the early evening, then gradual clearing, with a low around 71. Northeast wind 3 to 5 mph.
Wednesday
 
 Sunny, with a high near 89. Calm wind becoming northeast around 6 mph in the afternoon.
Wednesday Night
 
 Clear, with a low around 66. East wind around 5 mph becoming calm in the evening.
Thursday
 
 Sunny, with a high near 89. Light southeast wind.
Thursday Night
 
 Partly cloudy, with a low around 68. East wind around 5 mph becoming calm in the evening.
Friday
 
 Showers likely, with thunderstorms also possible after 1pm. Mostly cloudy, with a high near 86. Chance of precipitation is 60%.
Friday Night
 
 Showers likely and possibly a thunderstorm before 1am, then a chance of showers. Mostly cloudy, with a low around 69. Chance of precipitation is 60%.
Saturday
 
 A chance of showers, with thunderstorms also possible after 1pm. Partly sunny, with a high near 80. Chance of precipitation is 50%.
Saturday Night
 
 A chance of showers and thunderstorms before 1am, then a slight chance of showers. Mostly cloudy, with a low around 68. Chance of precipitation is 30%.
Sunday
 
 A slight chance of showers, then a chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 83. Chance of precipitation is 30%.
Sunday Night
 
 Partly cloudy, with a low around 68.
Monday
 
 A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 86.
Monday Night
 
 Mostly clear, with a low around 69.
Tuesday
 
 A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 90.

 

Forecast from NOAA-NWS for Arnold MO.