Castle Hill, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Castle Hill, a community in Contra Costa County, California.
This Afternoon
61°F
Light Rain
Rain. Mostly cloudy. High near 61, with temperatures falling to around 56 in the afternoon. South wind 3 to 7 mph. Chance of precipitation is 80%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Castle Hill
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 61°F | Light Rain | 3 to 7 mph S | 80% |
| Tonight | 48°F | Chance Light Rain then Mostly Cloudy | 5 mph ENE | 48% |
| Wednesday | 66°F | Sunny | 2 to 6 mph N | 1% |
| Wednesday Night | 47°F | Partly Cloudy | 1 to 5 mph W | 0% |
| Thursday | 71°F | Patchy Fog then Sunny | 1 to 5 mph N | 0% |
| Thursday Night | 48°F | Mostly Clear | 3 mph SW | 0% |
| Friday | 73°F | Sunny | 3 mph NNE | 0% |
| Friday Night | 49°F | Clear | 2 mph N | 0% |
| Saturday | 74°F | Sunny | 1 to 5 mph NE | 0% |
| Saturday Night | 50°F | Mostly Clear | 2 mph W | 0% |
| Sunday | 74°F | Mostly Sunny | 3 mph NW | 0% |
| Sunday Night | 51°F | Partly Cloudy | 2 mph WSW | 0% |
| Monday | 71°F | Partly Sunny | 3 mph SW | 1% |
| Monday Night | 50°F | Partly Cloudy | 3 mph SW | 1% |
Forecast source: National Weather Service (api.weather.gov) for Castle Hill (37.875, -122.059). Updated through the day.
Growing snapshot for Castle Hill
Last spring frost
Mar 8
First fall frost
Dec 22
Growing season
282 days
Hardiness zone
9b
More local growing data for Castle Hill: nearby ZIP 94595 weather · frost dates · planting calendar · California frost dates
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Climate data from the nearest NOAA station, Mt Diablo Junction, Ca (7.6 mi from Castle Hill). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 3, 2026.