National Weather Service Forecast for: Castro Valley CA
Issued by: National Weather Service San Francisco Bay Area/Monterey, CA
Updated: 12:26 am PST Feb 2, 2026
 
Overnight

Overnight: Mostly clear, with a low around 45. Light east wind.
Mostly Clear
 Monday

Monday: Sunny, with a high near 68. Calm wind becoming west northwest around 5 mph in the afternoon.
Sunny
 Monday
Night
Monday Night: Mostly clear, with a low around 44. Calm wind.
Mostly Clear
 Tuesday

Tuesday: Sunny, with a high near 70. Calm wind becoming northeast around 6 mph in the morning.
Sunny
 Tuesday
Night
Tuesday Night: Clear, with a low around 46. Light east northeast wind.
Clear
 Wednesday

Wednesday: Sunny, with a high near 71.
Sunny
 Wednesday
Night
Wednesday Night: Mostly clear, with a low around 46.
Mostly Clear
 Thursday

Thursday: Sunny, with a high near 70.
Sunny
 Thursday
Night
Thursday Night: Mostly cloudy, with a low around 48.
Mostly Cloudy
Lo 45 °F Hi 68 °F Lo 44 °F Hi 70 °F Lo 46 °F Hi 71 °F Lo 46 °F Hi 70 °F Lo 48 °F

 

Overnight
 
 Mostly clear, with a low around 45. Light east wind.
Monday
 
 Sunny, with a high near 68. Calm wind becoming west northwest around 5 mph in the afternoon.
Monday Night
 
 Mostly clear, with a low around 44. Calm wind.
Tuesday
 
 Sunny, with a high near 70. Calm wind becoming northeast around 6 mph in the morning.
Tuesday Night
 
 Clear, with a low around 46. Light east northeast wind.
Wednesday
 
 Sunny, with a high near 71.
Wednesday Night
 
 Mostly clear, with a low around 46.
Thursday
 
 Sunny, with a high near 70.
Thursday Night
 
 Mostly cloudy, with a low around 48.
Friday
 
 Mostly sunny, with a high near 69.
Friday Night
 
 Partly cloudy, with a low around 49.
Saturday
 
 Mostly sunny, with a high near 68.
Saturday Night
 
 Partly cloudy, with a low around 49.
Sunday
 
 A slight chance of rain. Mostly sunny, with a high near 68.

 

Forecast from NOAA-NWS for Castro Valley CA.