Castro Valley, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Castro Valley, a community in Alameda County, California.
Today
62°F
Light Rain
Rain. Mostly cloudy. High near 62, with temperatures falling to around 58 in the afternoon. South southwest wind 2 to 9 mph, with gusts as high as 18 mph. Chance of precipitation is 80%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Castro Valley
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 62°F | Light Rain | 2 to 9 mph SSW | 81% |
| Tonight | 49°F | Chance Light Rain then Mostly Cloudy | 5 mph E | 41% |
| Wednesday | 66°F | Sunny | 3 to 7 mph NNW | 1% |
| Wednesday Night | 50°F | Mostly Cloudy | 0 to 5 mph WNW | 0% |
| Thursday | 69°F | Sunny | 0 to 5 mph NNW | 0% |
| Thursday Night | 50°F | Mostly Clear | 0 to 5 mph NW | 0% |
| Friday | 72°F | Sunny | 1 to 5 mph NNE | 0% |
| Friday Night | 51°F | Mostly Clear | 0 to 3 mph NE | 0% |
| Saturday | 74°F | Sunny | 3 mph NE | 0% |
| Saturday Night | 53°F | Mostly Clear | 0 to 3 mph WSW | 0% |
| Sunday | 73°F | Mostly Sunny | 1 to 5 mph NNW | 0% |
| Sunday Night | 53°F | Mostly Cloudy | 0 to 5 mph N | 0% |
| Monday | 70°F | Partly Sunny | 1 to 6 mph SW | 1% |
| Monday Night | 52°F | Mostly Cloudy | 1 to 6 mph SW | 1% |
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 Nov 3, 2026.