Weather & Climate in Castro Valley, CA

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

Castro Valley enjoys a temperate climate with an average annual temperature of 60°F (15°C). Winters average 51°F in January while summers reach 66°F in July / relatively mild seasonal variation. The area gets 330 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 16.0 inches (drier than the 38-inch national average). Air quality is rated Good with a median AQI of 48. The city sits at an elevation of 348 feet.

Temperature

51°F Jan (11°C) 66°F Jul (19°C)

Annual Average	59.7°F
	11% above US avg
January Average	51°F (11°C)
July Average	66°F (19°C)
Sunny Days	330 days/yr

Geography

Elevation	348 ft (106 m)
Area	16.9 sq mi (43.8 km²)
Population Density	3,881/sq mi
Coordinates	37.7083°N, 122.0628°W
Timezone	America/Los_Angeles
County	San Mateo County County
Nearest Airport	Metro Oakland International (OAK) 9 miles away

Precipitation & Snow

Annual Rainfall 16.0"

58% below US avg

Wettest Month (Jan) 4.49"

Driest Month (Jul) 0.04"

Air Quality

AQI Median	48.0
Rating	Good

Natural Hazard Risk

Overall Risk	Relatively High
Risk Score	99.2 / 100
Social Vulnerability	20.5 / 100
Community Resilience	97.6 / 100

Hazard Breakdown

Tornado	Relatively Low
Earthquake	Relatively High
Wildfire	Relatively Moderate
Flood	Relatively High
Hail	Very Low
Strong Wind	Relatively Low
Heat Wave	Relatively Moderate
Winter Weather	Very Low
Lightning	Relatively Moderate
Drought	Relatively High
Cold Wave	No Rating
Landslide	Relatively High
Coastal Flood	Relatively High
Tsunami	Relatively Moderate

Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

6,019 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M6.0.

Aug 24, 2014	The 2014 South Napa, California Earthquake	M6.0	61 km	11 km
Apr 18, 1990	5 km NNW of Aromas, California	M5.4	93 km	5 km
Aug 12, 1998	10 km SW of Ridgemark, California	M5.1	119 km	9 km
Apr 18, 1990	4 km E of Interlaken, California	M5.1	90 km	7 km
Jan 16, 1993	9 km E of Gilroy, California	M4.9	93 km	7 km
May 14, 2002	5 km SSW of Gilroy, California	M4.9	92 km	7 km
Apr 23, 1995	22 km NNE of Soledad, California	M4.9	145 km	7 km
Sep 3, 2000	5 km WSW of Yountville, California	M4.9	81 km	9 km
Apr 19, 1996	2 km E of Aromas, California	M4.9	100 km	5 km
Apr 18, 1990	4 km NNW of Aromas, California	M4.9	94 km	6 km
Sep 4, 1995	13 km SW of Middletown, California	M4.8	124 km	7 km
May 12, 2006	7 km W of Cobb, California	M4.7	140 km	4 km
May 21, 1996	8 km ESE of East Foothills, California	M4.7	49 km	8 km
Apr 18, 1990	4 km N of Aromas, California	M4.7	94 km	4 km
Aug 11, 1993	14 km ESE of Alum Rock, California	M4.7	56 km	9 km
Jan 2, 2025	4 km NW of Cobb, CA	M4.7	140 km	1 km
Aug 27, 2011	21 km NE of Soledad, California	M4.6	147 km	8 km
Aug 18, 1999	0 km S of Bolinas, California	M4.6	59 km	8 km
Mar 24, 1991	1 km NNE of Interlaken, California	M4.6	88 km	15 km
Jan 11, 2000	6 km N of Geyserville, California	M4.6	139 km	6 km

Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

63 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2. Total: 9 injuries.

Date	Rating	Distance	Path	Fatalities
May 5, 1998	EF2	38 km	0.6 mi	0
Apr 27, 1953	EF2	94 km	0.1 mi	0
Jan 11, 1951	EF2	38 km	5.7 mi	0
Dec 14, 2024	EF1	73 km	0.3 mi	0
Jan 23, 2010	EF1	35 km	1.6 mi	0
Apr 14, 2006	EF1	94 km	0.5 mi	0
Mar 20, 2005	EF1	32 km	3.0 mi	0
Dec 20, 2001	EF1	86 km	0.5 mi	0
Dec 5, 1998	EF1	100 km	1.5 mi	0
May 5, 1998	EF1	37 km	0.3 mi	0
Dec 23, 1996	EF1	97 km	6.0 mi	0
Apr 19, 1988	EF1	95 km	0.2 mi	0
Feb 27, 1983	EF1	100 km	0.8 mi	0
Jan 14, 1980	EF1	30 km	0.3 mi	0
Mar 1, 1978	EF1	100 km	1.5 mi	0
May 31, 1967	EF1	73 km	0.1 mi	0
Apr 1, 1965	EF1	84 km	0.1 mi	0
Apr 1, 1958	EF1	27 km	0.2 mi	0
Nov 8, 2022	EF0	95 km	0.8 mi	0
Jan 6, 2019	EF0	83 km	0.1 mi	0

Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Tsunami History

5 tsunamis recorded within 500 km. Highest wave on record: 4.5 m (15 ft).

Year	Location	Cause	Max Wave	Deaths	Distance
1868	N. CALIFORNIA	Eruption + Earthquake	4.5 m	30	3 km
1989	N. CALIFORNIA	Earthquake	1.0 m	62	76 km
1856	N. CALIFORNIA	Eruption + Earthquake	0.6 m	—	31 km
1906	N. CALIFORNIA	Eruption + Earthquake	0.1 m	—	39 km
1865	N. CALIFORNIA	Eruption + Earthquake	—	—	58 km

Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

1 volcano within 200 km. Closest: Clear Lake (153 km).

Name	Type	Elevation	Last Eruption	Distance
Clear Lake	Volcanic field	1,439 m (4,721 ft)	Unknown	153 km

Source: Smithsonian Institution Global Volcanism Program (GVP).

Wildfire History

20 wildfires (100+ acres) recorded within 100 km. Largest: SCU LIGHTNING COMPLEX (405,787 acres, 2020).

Year	Name	Acres Burned	Distance
2020	SCU LIGHTNING COMPLEX	405,787	55 km
2020	CZU AUG LIGHTNING	85,894	64 km
2017	NUNS	56,883	81 km
2017	ATLAS	51,664	75 km
2007	LICK	47,424	78 km
2006	CANYON	36,851	74 km
1988	MILLER	35,750	80 km
2003	ANNIE	17,383	90 km
2024	CORRAL	16,138	54 km
2009	CORRAL	12,006	52 km
1995	VISION	11,931	80 km
1985	LEXINGTON	11,550	64 km
2015	WRAGG	8,455	86 km
2009	LOCKHEED	8,287	71 km
2003	BIRD	7,727	66 km
2014	MONTICELLO	6,984	92 km
1984	SITE 300 3	6,911	52 km
2005	TESLA	6,638	44 km
2003	DEL PUERTO	6,441	66 km
2016	COLD	6,289	92 km

Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month	Avg Temperature	Precipitation	Summary
January	51°F (11°C)	4.5 in	Wettest
February	51°F (11°C)	3.8 in
March	53°F (12°C)	3.4 in
April	57°F (14°C)	1.4 in
May	60°F (16°C)	0.5 in
June	64°F (18°C)	0.1 in
July	66°F (19°C)	0.0 in	Driest
August	68°F (20°C)	0.1 in	Warmest
September	67°F (20°C)	0.3 in
October	63°F (17°C)	1.3 in
November	55°F (13°C)	3.1 in
December	49°F (9°C)	3.3 in	Coldest

Castro Valley has a seasonal temperature swing of 19°F / from 49°F in December to 68°F in August. Total annual precipitation is 21.8 inches, with January being the wettest month (4.5") and July the driest (0.0").

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