National Weather Service Forecast for: Castro Valley CA
Issued by: National Weather Service San Francisco Bay Area/Monterey, CA
Updated: 1:26 am PDT Jun 22, 2026
 
Overnight

Overnight: Mostly cloudy, with a low around 55. West wind around 5 mph.
Mostly Cloudy
 Monday

Monday: Cloudy through mid morning, then gradual clearing, with a high near 76. Light west southwest wind becoming west 5 to 10 mph in the morning.
Becoming
Sunny
 Monday
Night
Monday Night: Increasing clouds, with a low around 56. West wind 5 to 8 mph becoming calm after midnight.
Increasing
Clouds
 Tuesday

Tuesday: Cloudy through mid morning, then gradual clearing, with a high near 79. Calm wind becoming west 5 to 9 mph in the afternoon.
Becoming
Sunny
 Tuesday
Night
Tuesday Night: Partly cloudy, with a low around 56. West wind 5 to 8 mph becoming calm in the evening.
Partly Cloudy
 Wednesday

Wednesday: Mostly sunny, with a high near 80.
Mostly Sunny
 Wednesday
Night
Wednesday Night: Mostly clear, with a low around 57.
Mostly Clear
 Thursday

Thursday: Sunny, with a high near 76.
Sunny
 Thursday
Night
Thursday Night: Partly cloudy, with a low around 56.
Partly Cloudy
Lo 55 °F Hi 76 °F Lo 56 °F Hi 79 °F Lo 56 °F Hi 80 °F Lo 57 °F Hi 76 °F Lo 56 °F

 

Overnight
 
 Mostly cloudy, with a low around 55. West wind around 5 mph.
Monday
 
 Cloudy through mid morning, then gradual clearing, with a high near 76. Light west southwest wind becoming west 5 to 10 mph in the morning.
Monday Night
 
 Increasing clouds, with a low around 56. West wind 5 to 8 mph becoming calm after midnight.
Tuesday
 
 Cloudy through mid morning, then gradual clearing, with a high near 79. Calm wind becoming west 5 to 9 mph in the afternoon.
Tuesday Night
 
 Partly cloudy, with a low around 56. West wind 5 to 8 mph becoming calm in the evening.
Wednesday
 
 Mostly sunny, with a high near 80.
Wednesday Night
 
 Mostly clear, with a low around 57.
Thursday
 
 Sunny, with a high near 76.
Thursday Night
 
 Partly cloudy, with a low around 56.
Friday
 
 Mostly sunny, with a high near 72.
Friday Night
 
 Partly cloudy, with a low around 57.
Saturday
 
 Mostly sunny, with a high near 71.
Saturday Night
 
 Mostly clear, with a low around 55.
Sunday
 
 Sunny, with a high near 78.

 

Forecast from NOAA-NWS for Castro Valley CA.