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Weather & Climate in Castle Hill, CA

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

Castle Hill enjoys a temperate climate with an average annual temperature of 62°F (17°C). Winters average 50°F in January while summers reach 73°F in July. 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 17.7 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 204 feet.

Temperature

50°F Jan (10°C) 73°F Jul (23°C)
Annual Average62.4°F
16% above US avg
January Average50°F (10°C)
July Average73°F (23°C)
Sunny Days330 days/yr

Geography

Elevation204 ft (62 m)
Area0.6 sq mi (1.5 km²)
Population Density2,208/sq mi
Coordinates37.8747°N, 122.0586°W
TimezoneAmerica/Los_Angeles
CountySan Mateo County County
Nearest AirportMetro Oakland International (OAK)
14 miles away

Precipitation & Snow

Annual Rainfall 17.7"
53% below US avg
Snowfall 0.0"
Wettest Month (Jan) 4.65"
Driest Month (Jul) 0.04"

Air Quality

AQI Median48.0
RatingGood

Natural Hazard Risk

Overall RiskRelatively High
Risk Score99.2 / 100
Social Vulnerability20.5 / 100
Community Resilience97.6 / 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

5,374 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 44 km 11 km
Apr 18, 1990 5 km NNW of Aromas, California M5.4 111 km 5 km
Apr 18, 1990 4 km E of Interlaken, California M5.1 107 km 7 km
Aug 12, 1998 10 km SW of Ridgemark, California M5.1 135 km 9 km
Jan 16, 1993 9 km E of Gilroy, California M4.9 109 km 7 km
Apr 19, 1996 2 km E of Aromas, California M4.9 117 km 5 km
May 14, 2002 5 km SSW of Gilroy, California M4.9 109 km 7 km
Sep 3, 2000 5 km WSW of Yountville, California M4.9 64 km 9 km
Apr 18, 1990 4 km NNW of Aromas, California M4.9 111 km 6 km
Sep 4, 1995 13 km SW of Middletown, California M4.8 108 km 7 km
May 12, 2006 7 km W of Cobb, California M4.7 124 km 4 km
May 21, 1996 8 km ESE of East Foothills, California M4.7 65 km 8 km
Apr 18, 1990 4 km N of Aromas, California M4.7 112 km 4 km
Aug 11, 1993 14 km ESE of Alum Rock, California M4.7 71 km 9 km
Jan 2, 2025 4 km NW of Cobb, CA M4.7 124 km 1 km
Aug 18, 1999 0 km S of Bolinas, California M4.6 55 km 8 km
Mar 24, 1991 1 km NNE of Interlaken, California M4.6 105 km 15 km
Jan 11, 2000 6 km N of Geyserville, California M4.6 124 km 6 km
Feb 18, 2004 4 km WNW of Cobb, California M4.6 124 km 3 km
Jan 12, 2014 8 km W of Cobb, California M4.5 124 km 2 km
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

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

Date Rating Distance Path Fatalities
May 5, 1998 EF2 56 km 0.6 mi 0
Jun 1, 1958 EF2 92 km 15.0 mi 0
Apr 27, 1953 EF2 96 km 0.1 mi 0
Jan 11, 1951 EF2 56 km 5.7 mi 0
Dec 14, 2024 EF1 92 km 0.3 mi 0
Mar 18, 2011 EF1 86 km 0.1 mi 0
Jan 23, 2010 EF1 26 km 1.6 mi 0
Apr 14, 2006 EF1 96 km 0.5 mi 0
Mar 20, 2005 EF1 40 km 3.0 mi 0
Dec 5, 1998 EF1 85 km 1.5 mi 0
May 5, 1998 EF1 55 km 0.3 mi 0
Dec 23, 1996 EF1 87 km 6.0 mi 0
Feb 22, 1996 EF1 95 km 1.0 mi 0
Dec 2, 1992 EF1 94 km 7.5 mi 0
Dec 2, 1992 EF1 89 km 1.0 mi 0
Apr 19, 1988 EF1 86 km 0.2 mi 0
Feb 27, 1983 EF1 85 km 0.8 mi 0
Jan 14, 1980 EF1 47 km 0.3 mi 0
May 31, 1967 EF1 67 km 0.1 mi 0
Nov 10, 1964 EF1 98 km 1.0 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 20 km
1989 N. CALIFORNIA Earthquake 1.0 m 62 95 km
1856 N. CALIFORNIA Eruption + Earthquake 0.6 m — 47 km
1906 N. CALIFORNIA Eruption + Earthquake 0.1 m — 43 km
1865 N. CALIFORNIA Eruption + Earthquake — — 76 km
Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

1 volcano within 200 km. Closest: Clear Lake (137 km).

Name Type Elevation Last Eruption Distance
Clear Lake Volcanic field 1,439 m (4,721 ft) Unknown 137 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 65 km
2020 HENNESSEY 314,241 86 km
2018 COUNTY 92,450 90 km
2020 CZU AUG LIGHTNING 85,894 82 km
2020 GLASS 68,020 87 km
2017 NUNS 56,883 66 km
2017 ATLAS 51,664 57 km
2007 LICK 47,424 91 km
2004 RUMSEY 39,335 100 km
2017 TUBBS 36,981 94 km
2006 CANYON 36,851 85 km
1988 MILLER 35,750 62 km
2024 CORRAL 16,138 59 km
2006 ZAM ASSIST 14,404 99 km
2009 CORRAL 12,006 59 km
1995 VISION 11,931 73 km
1985 LEXINGTON 11,550 82 km
2015 WRAGG 8,455 67 km
2009 LOCKHEED 8,287 89 km
2003 BIRD 7,727 73 km
Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 50°F (10°C) 4.7 in Wettest
February 51°F (11°C) 3.9 in
March 54°F (12°C) 3.2 in
April 57°F (14°C) 1.3 in
May 62°F (17°C) 0.5 in
June 67°F (19°C) 0.1 in
July 73°F (23°C) 0.0 in Warmest, Driest
August 70°F (21°C) 0.1 in
September 68°F (20°C) 0.3 in
October 63°F (17°C) 1.2 in
November 54°F (12°C) 3.2 in
December 48°F (9°C) 3.3 in Coldest

Castle Hill has a seasonal temperature swing of 26°F / from 48°F in December to 73°F in July. Total annual precipitation is 21.8 inches, with January being the wettest month (4.7") and July the driest (0.0").

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