Harman US

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.

Tonight
56°F
Mostly Clear
Mostly clear. Low around 56, with temperatures rising to around 58 overnight. South southwest wind around 7 mph.

7-day forecast for Castle Hill

WhenTempForecastWindPrecip
Tonight 56°F Mostly Clear 7 mph SSW 0%
Saturday 87°F Sunny 3 to 7 mph SW 0%
Saturday Night 57°F Partly Cloudy 7 mph SSW 0%
Sunday 78°F Partly Sunny 8 mph SW 3%
Sunday Night 56°F Mostly Cloudy 8 mph SW 3%
Monday 80°F Mostly Sunny 6 to 9 mph WSW 0%
Monday Night 56°F Mostly Clear 5 to 9 mph SW 0%
Tuesday 84°F Sunny 3 to 7 mph WSW 0%
Tuesday Night 57°F Mostly Clear 1 to 7 mph SW 0%
Wednesday 95°F Sunny 0 to 5 mph WSW 0%
Wednesday Night 62°F Mostly Clear 1 to 5 mph SW 0%
Thursday 96°F Sunny 0 to 7 mph WSW 0%
Thursday Night 62°F Mostly Clear 3 to 7 mph WSW 0%
Friday 88°F Sunny 3 to 7 mph SW 0%

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

Nearby towns & communities

All California locations ›

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 Sep 19, 2026.