Castro Valley, CA Weather & Growing Conditions
This Afternoon
80°F
Sunny
Sunny. High near 80, with temperatures falling to around 74 in the afternoon. West wind around 9 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 80°F | Sunny | 9 mph W | 0% |
| Tonight | 55°F | Mostly Cloudy | 8 mph WSW | 0% |
| Sunday | 71°F | Mostly Cloudy | 6 to 9 mph WSW | 0% |
| Sunday Night | 56°F | Mostly Cloudy | 8 mph WSW | 1% |
| Monday | 73°F | Mostly Sunny | 7 to 10 mph WSW | 0% |
| Monday Night | 55°F | Mostly Cloudy | 5 to 10 mph WSW | 0% |
| Tuesday | 75°F | Mostly Sunny | 5 to 9 mph WSW | 0% |
| Tuesday Night | 55°F | Partly Cloudy | 1 to 9 mph SW | 0% |
| Wednesday | 86°F | Mostly Sunny | 1 to 7 mph SW | 0% |
| Wednesday Night | 60°F | Partly Cloudy | 1 to 7 mph SW | 0% |
| Thursday | 89°F | Mostly Sunny | 1 to 8 mph SSW | 0% |
| Thursday Night | 60°F | Partly Cloudy | 2 to 8 mph WSW | 0% |
| Friday | 81°F | Mostly Sunny | 2 to 9 mph WSW | 0% |
| Friday Night | 57°F | Partly Cloudy | 3 to 9 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 Sep 20, 2026.