Castro Valley, CA Weather & Growing Conditions
Overnight
57°F
Mostly Clear
Mostly clear, with a low around 57. West wind around 2 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 57°F | Mostly Clear | 2 mph W | 0% |
| Tuesday | 90°F | Haze then Sunny | 2 to 9 mph WSW | 0% |
| Tuesday Night | 57°F | Mostly Clear | 2 to 9 mph W | 0% |
| Wednesday | 88°F | Mostly Sunny | 3 to 9 mph W | 0% |
| Wednesday Night | 58°F | Partly Cloudy | 2 to 9 mph W | 0% |
| Thursday | 86°F | Mostly Sunny | 2 to 9 mph W | 0% |
| Thursday Night | 59°F | Partly Cloudy | 3 to 9 mph W | 0% |
| Friday | 89°F | Mostly Sunny | 3 to 9 mph W | 0% |
| Friday Night | 61°F | Partly Cloudy | 3 to 9 mph WSW | 0% |
| Saturday | 89°F | Sunny | 3 to 9 mph WSW | 0% |
| Saturday Night | 62°F | Mostly Clear | 6 to 9 mph WSW | 0% |
| Sunday | 83°F | Sunny | 6 to 10 mph WSW | 0% |
| Sunday Night | 58°F | Partly Cloudy | 12 mph WSW | 0% |
| Monday | 78°F | Mostly Sunny | 12 mph WSW | 0% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Castro Valley, CA
Last spring frost
Jan 2
First fall frost
Dec 25
Growing season
365 days
Hardiness zone
9b
Explore more for Castro Valley, CA: full frost dates · planting calendar · California frost dates
Climate data from the nearest NOAA station, Hayward Air Terminal, Ca (6.9 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.