Castro Valley, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Castro Valley, a community in Alameda County, California.
Tonight
57°F
Mostly Cloudy
Mostly cloudy, with a low around 57. Southwest wind around 5 mph.
7-day forecast for Castro Valley
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 57°F | Mostly Cloudy | 5 mph SW | 0% |
| Saturday | 80°F | Mostly Sunny | 3 to 8 mph WSW | 0% |
| Saturday Night | 57°F | Mostly Cloudy | 6 mph WSW | 0% |
| Sunday | 72°F | Mostly Cloudy | 5 to 8 mph WSW | 4% |
| Sunday Night | 57°F | Mostly Cloudy | 5 to 8 mph WSW | 4% |
| Monday | 75°F | Partly Sunny | 5 to 9 mph WSW | 0% |
| Monday Night | 57°F | Partly Cloudy | 3 to 9 mph WSW | 0% |
| Tuesday | 79°F | Mostly Sunny | 3 to 8 mph SW | 0% |
| Tuesday Night | 57°F | Partly Cloudy | 1 to 8 mph SW | 0% |
| Wednesday | 90°F | Sunny | 1 to 7 mph SW | 0% |
| Wednesday Night | 61°F | Mostly Clear | 0 to 7 mph WSW | 0% |
| Thursday | 90°F | Sunny | 0 to 8 mph WSW | 0% |
| Thursday Night | 61°F | Partly Cloudy | 2 to 8 mph WSW | 0% |
| Friday | 82°F | Mostly Sunny | 2 to 8 mph WSW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Castro Valley (37.708, -122.063). Updated through the day.
Growing snapshot for Castro Valley
Last spring frost
Jan 2
First fall frost
Dec 25
Growing season
365 days
Hardiness zone
10a
More local growing data for Castro Valley: nearby ZIP 94541 weather · frost dates · planting calendar · California frost dates
Nearby towns & communities
Alameda
Albany
Ashland
Berkeley
Camino Tassajara
Cherryland
Dublin
Emeryville
Fairview
Fremont
Hayward
Kensington
Livermore
Mountain House
Newark
Oakland
Piedmont
Pleasanton
San Leandro
San Lorenzo
Sunol
Union City
Climate data from the nearest NOAA station, Hayward Air Terminal, Ca (2 mi from Castro Valley). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.