Sign In Register

Weather & Climate in Union City, CA

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

Union City enjoys a temperate climate with an average annual temperature of 60°F (15°C). Winters average 51°F in January while summers reach 67°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 15.9 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 95 feet.

Temperature

51°F Jan (10°C) 67°F Jul (20°C)
Annual Average59.5°F
10% above US avg
January Average51°F (10°C)
July Average67°F (20°C)
Sunny Days330 days/yr

Geography

Elevation95 ft (29 m)
Area19.4 sq mi (50.2 km²)
Population Density3,512/sq mi
Coordinates37.6028°N, 122.0188°W
TimezoneAmerica/Los_Angeles
CountySan Mateo County County
Nearest AirportMetro Oakland International (OAK)
14 miles away

Precipitation & Snow

Annual Rainfall 15.9"
58% below US avg
Snowfall 0.0"
Wettest Month (Jan) 3.19"
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

5,010 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 73 km 11 km
Apr 18, 1990 5 km NNW of Aromas, California M5.4 81 km 5 km
Apr 18, 1990 4 km E of Interlaken, California M5.1 78 km 7 km
Aug 12, 1998 10 km SW of Ridgemark, California M5.1 107 km 9 km
Jan 16, 1993 9 km E of Gilroy, California M4.9 82 km 7 km
May 14, 2002 5 km SSW of Gilroy, California M4.9 80 km 7 km
Apr 18, 1990 4 km NNW of Aromas, California M4.9 81 km 6 km
Apr 19, 1996 2 km E of Aromas, California M4.9 88 km 5 km
Apr 23, 1995 22 km NNE of Soledad, California M4.9 133 km 7 km
Sep 3, 2000 5 km WSW of Yountville, California M4.9 93 km 9 km
Sep 4, 1995 13 km SW of Middletown, California M4.8 136 km 7 km
May 21, 1996 8 km ESE of East Foothills, California M4.7 38 km 8 km
Apr 18, 1990 4 km N of Aromas, California M4.7 82 km 4 km
Aug 11, 1993 14 km ESE of Alum Rock, California M4.7 44 km 9 km
Aug 27, 2011 21 km NE of Soledad, California M4.6 136 km 8 km
Mar 24, 1991 1 km NNE of Interlaken, California M4.6 76 km 15 km
Aug 18, 1999 0 km S of Bolinas, California M4.6 68 km 8 km
Sep 19, 2023 15 km SW of Westley, CA M4.5 66 km 4 km
Aug 3, 2006 5 km W of Glen Ellen, California M4.5 98 km 9 km
Jan 12, 2011 9 km SSE of San Juan Bautista, California M4.5 103 km 8 km
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

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

Date Rating Distance Path Fatalities
May 5, 1998 EF2 26 km 0.6 mi 0
Mar 11, 1985 EF2 100 km 0.5 mi 0
Apr 27, 1953 EF2 90 km 0.1 mi 0
Jan 11, 1951 EF2 27 km 5.7 mi 0
Dec 14, 2024 EF1 62 km 0.3 mi 0
Jan 23, 2010 EF1 41 km 1.6 mi 0
Apr 14, 2006 EF1 90 km 0.5 mi 0
Mar 20, 2005 EF1 36 km 3.0 mi 0
Dec 20, 2001 EF1 74 km 0.5 mi 0
May 5, 1998 EF1 26 km 0.3 mi 0
Apr 19, 1988 EF1 99 km 0.2 mi 0
Jan 14, 1980 EF1 18 km 0.3 mi 0
Mar 1, 1978 EF1 96 km 1.5 mi 0
May 31, 1967 EF1 75 km 0.1 mi 0
Apr 1, 1965 EF1 72 km 0.1 mi 0
Apr 1, 1958 EF1 29 km 0.2 mi 0
Jan 6, 2019 EF0 72 km 0.1 mi 0
Jan 6, 2019 EF0 72 km 0.5 mi 0
Jan 6, 2016 EF0 93 km 0.6 mi 0
Dec 24, 2015 EF0 94 km 0.2 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 13 km
1989 N. CALIFORNIA Earthquake 1.0 m 62 64 km
1856 N. CALIFORNIA Eruption + Earthquake 0.6 m — 27 km
1906 N. CALIFORNIA Eruption + Earthquake 0.1 m — 44 km
1865 N. CALIFORNIA Eruption + Earthquake — — 46 km
Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

1 volcano within 200 km. Closest: Clear Lake (166 km).

Name Type Elevation Last Eruption Distance
Clear Lake Volcanic field 1,439 m (4,721 ft) Unknown 166 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 47 km
2020 CZU AUG LIGHTNING 85,894 54 km
2017 NUNS 56,883 93 km
2017 ATLAS 51,664 87 km
2007 LICK 47,424 67 km
2006 CANYON 36,851 65 km
1988 MILLER 35,750 92 km
2003 ANNIE 17,383 80 km
2024 CORRAL 16,138 49 km
2009 CORRAL 12,006 47 km
1995 VISION 11,931 89 km
1985 LEXINGTON 11,550 52 km
2015 WRAGG 8,455 98 km
2009 LOCKHEED 8,287 60 km
2003 BIRD 7,727 61 km
1984 SITE 300 3 6,911 48 km
2005 TESLA 6,638 41 km
2003 DEL PUERTO 6,441 58 km
2006 MIDWAY 6,243 44 km
2020 CREWS 5,802 82 km
Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 51°F (10°C) 3.2 in Wettest
February 53°F (12°C) 2.7 in
March 55°F (13°C) 2.6 in
April 58°F (14°C) 1.1 in
May 61°F (16°C) 0.3 in
June 65°F (18°C) 0.1 in
July 67°F (20°C) 0.0 in Driest
August 67°F (20°C) 0.1 in Warmest
September 67°F (19°C) 0.2 in
October 63°F (17°C) 1.0 in
November 55°F (13°C) 2.3 in
December 49°F (10°C) 2.3 in Coldest

Union City has a seasonal temperature swing of 18°F / from 49°F in December to 67°F in August. Total annual precipitation is 15.9 inches, with January being the wettest month (3.2") and July the driest (0.0").

View full profile of Union City, CA →