Home › Cities › United States › California › Castro Valley › Tools › Climate zone
Castro Valley has a warm-summer Mediterranean climate.
Mild, rainy winters and hot, dry summers — here's what that means in plain terms.
What this climate feels like
The four things a regular visitor actually wants to know:
Highs near 77°F in August. About 10 days a year above 90 °F.
Lows near 43°F in January. About 2 freezing nights a year.
About 14 in of rain a year. Wettest in February.
A roughly even mix of sun and cloud.
What "warm-summer Mediterranean" means
Climate scientists sort every place on Earth into about 30 climate types, based on how hot, cold, wet and dry it is across the year. Castro Valley's type — warm-summer mediterranean — sits in the broad family of mild, temperate climates.
Researchers write climate types as a short letter code. Here is what each letter means:
Cities with the same climate as Castro Valley
A warm-summer Mediterranean climate (Csb) — these recognizable cities share it. If you know one of them, you know roughly what to expect.
Has Castro Valley's climate type changed?
Stable — Castro Valley's climate has held the same type between the 1971–2000 and 1991–2020 normals. The label is steady; the climate beneath it is still warming.
What this climate means for you
Cool-season vegetables, stone fruit, berries and hops excel. Wine grapes do well at the warmer end.
Late spring through early autumn is the pristine window — warm, dry, sunny. Winter is wet but never brutal.
Comfortable year-round — sunny, dry summers and mild, wet winters. Heating is modest; AC is rarely necessary.
Where these numbers come from
The climate type and the month-by-month figures on this page are computed from Castro Valley's measured 30-year climate normals (1991–2020) — the same official records behind Castro Valley's main climate page, so the two always agree.
Long-range climate maps measure things slightly differently and can place a city in a neighbouring category. Where they differ, this page uses the measured station record as the climate today.
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Newark (NOAA GHCN station USC00046144), about 21 km from the city centre.