National Weather Service Forecast for: Castro Valley CA
Issued by: National Weather Service San Francisco Bay Area/Monterey, CA
Updated: 2:07 am PDT Sep 13, 2026
 
Today

Today: Sunny, with a high near 72. West wind 7 to 11 mph, with gusts as high as 18 mph.
Sunny
 Tonight

Tonight: Partly cloudy, with a low around 55. West wind 5 to 7 mph becoming calm in the evening.
Partly Cloudy
 Monday

Monday: Partly sunny, then gradually becoming sunny, with a high near 81. Calm wind becoming west 5 to 9 mph in the afternoon.
Becoming
Sunny
 Monday
Night
Monday Night: Mostly clear, with a low around 56. West wind 5 to 8 mph becoming calm in the evening.
Mostly Clear
 Tuesday

Tuesday: Mostly sunny, with a high near 80. Calm wind becoming west 5 to 8 mph in the afternoon.
Mostly Sunny
 Tuesday
Night
Tuesday Night: Partly cloudy, with a low around 58.
Partly Cloudy
 Wednesday

Wednesday: Mostly sunny, with a high near 79.
Mostly Sunny
 Wednesday
Night
Wednesday Night: Mostly clear, with a low around 58.
Mostly Clear
 Thursday

Thursday: Mostly sunny, with a high near 81.
Mostly Sunny
Hi 72 °F Lo 55 °F Hi 81 °F Lo 56 °F Hi 80 °F Lo 58 °F Hi 79 °F Lo 58 °F Hi 81 °F

 

Today
 
 Sunny, with a high near 72. West wind 7 to 11 mph, with gusts as high as 18 mph.
Tonight
 
 Partly cloudy, with a low around 55. West wind 5 to 7 mph becoming calm in the evening.
Monday
 
 Partly sunny, then gradually becoming sunny, with a high near 81. Calm wind becoming west 5 to 9 mph in the afternoon.
Monday Night
 
 Mostly clear, with a low around 56. West wind 5 to 8 mph becoming calm in the evening.
Tuesday
 
 Mostly sunny, with a high near 80. Calm wind becoming west 5 to 8 mph in the afternoon.
Tuesday Night
 
 Partly cloudy, with a low around 58.
Wednesday
 
 Mostly sunny, with a high near 79.
Wednesday Night
 
 Mostly clear, with a low around 58.
Thursday
 
 Mostly sunny, with a high near 81.
Thursday Night
 
 Mostly clear, with a low around 58.
Friday
 
 Mostly sunny, with a high near 79.
Friday Night
 
 Partly cloudy, with a low around 58.
Saturday
 
 Mostly sunny, with a high near 75.

 

Forecast from NOAA-NWS for Castro Valley CA.