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Monthly climate in Castro Valley, California, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Castro Valley features a warm-summer Mediterranean climate (Csb).Temperatures typically range between 10 °C (50 °F) and 20 °C (69 °F) through the year, but rarely can drop to -2 °C (29 °F) or can rise to as high as 42 °C (107 °F).The average annual precipitation amounts to about 446 mm (17.6 inches) and receives 48 rainy days on the 1 mm (0.04 inches) threshold annually.Castro Valley enjoys an average of 3452 hours of sunshine throughout the year, and daylight varies from 9 hours 35 minutes to 14 hours 42 minutes per day.

Monthly average temperatures in Castro Valley, California, United States §

The warmest months in Castro Valley are July, August and September, with daily mean temperatures ranging from 20 to 20 °C (68 - 69 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 10 to 11 °C (50 - 52 °F) throughout the day. On average each year, Castro Valley experiences 92 days above 25 °C (77.0 °F) and 1 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Castro Valley, California, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to June 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum 25°C
(77°F)		 26°C
(79°F)		 28°C
(82°F)		 31°C
(88°F)		 35°C
(94°F)		 38°C
(101°F)		 35°C
(95°F)		 40°C
(104°F)		 42°C
(107°F)		 34°C
(93°F)		 27°C
(81°F)		 22°C
(73°F)
Mean maximum 19°C
(66°F)		 22°C
(72°F)		 26°C
(78°F)		 29°C
(84°F)		 31°C
(88°F)		 35°C
(95°F)		 33°C
(91°F)		 36°C
(96°F)		 37°C
(98°F)		 31°C
(87°F)		 24°C
(76°F)		 19°C
(67°F)
Average high 14°C
(58°F)		 17°C
(62°F)		 18°C
(64°F)		 20°C
(69°F)		 23°C
(73°F)		 26°C
(79°F)		 27°C
(81°F)		 27°C
(82°F)		 27°C
(81°F)		 24°C
(76°F)		 19°C
(66°F)		 14°C
(58°F)
Daily mean 10°C
(50°F)		 11°C
(52°F)		 12°C
(54°F)		 14°C
(58°F)		 16°C
(61°F)		 19°C
(66°F)		 20°C
(68°F)		 20°C
(69°F)		 20°C
(68°F)		 17°C
(63°F)		 13°C
(55°F)		 10°C
(50°F)
Average low 6°C
(43°F)		 6°C
(43°F)		 7°C
(45°F)		 9°C
(48°F)		 11°C
(52°F)		 13°C
(56°F)		 14°C
(57°F)		 15°C
(59°F)		 14°C
(57°F)		 11°C
(52°F)		 8°C
(46°F)		 6°C
(42°F)
Mean minimum -0°C
(32°F)		 0°C
(33°F)		 2°C
(36°F)		 4°C
(40°F)		 7°C
(45°F)		 9°C
(49°F)		 12°C
(54°F)		 12°C
(55°F)		 9°C
(49°F)		 6°C
(43°F)		 3°C
(37°F)		 1°C
(34°F)
Minimum -2°C
(29°F)		 -1°C
(30°F)		 1°C
(35°F)		 3°C
(37°F)		 5°C
(40°F)		 8°C
(47°F)		 11°C
(52°F)		 12°C
(53°F)		 6°C
(44°F)		 4°C
(40°F)		 2°C
(35°F)		 -1°C
(30°F)

Compare climate in Castro Valley with other places

Compare temperature, precipitation, sunshine, UV index in Castro Valley, California, United States with other places around the world.

Monthly average precipitation in Castro Valley, California, United States §

Castro Valley usually has the most precipitation in January, February and March, with an average of 8 rainy days and 87 mm (3.4 inches) of precipitation per month.The driest months in Castro Valley are June, July and August. On average, 1 mm (0.0 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Castro Valley, California, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average precipitation mm (inches) 94 (3.7) 89 (3.5) 77 (3.0) 30 (1.2) 17 (0.7) 2 (0.1) 0 (0.0) 0 (0.0) 2 (0.1) 22 (0.9) 38 (1.5) 76 (3.0)
Average precipitation days (≥ 1 mm) 8 7 10 5 2 0 0 0 0 2 5 9

Monthly sunshine hours in Castro Valley, California, United States §

The sunniest months in Castro Valley are May, June and July, when the sun shines an average of 12 hours 13 minutes a day.Least sunny months in Castro Valley: January, February and December receive an average of 6 hours 21 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Castro Valley, California, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean monthly sunshine hours 158 221 267 302 363 376 384 350 312 285 230 199
Mean daily daylight hours 9h 53m 10h 48m 11h 59m 13h 11m 14h 12m 14h 42m 14h 26m 13h 31m 12h 22m 11h 9m 10h 7m 9h 35m

Solar UV radiation in Castro Valley, California, United States §

Castro Valley experiences the highest level of ultraviolet (UV) radiation in June, July and August, when the maximum UV index can reach values of 10 - 11, which corresponds to the Very High / Extreme category of sun exposure.January, February and December are in the Moderate exposure category. In these months, the maximum values of the UV index do not exceed 5. For more detailed information, check out our hourly Castro Valley UV Index data.

Average daily maximum UV levels by month for Castro Valley, California, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2022 to January 2023.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
UV Index (month maximum) 3 5 8 9 10 11 11 10 9 7 5 3