Union City, CA
Full City Profile · California · San Mateo County County
3.8
/5.0
B+
Good
68,141
Population
3,512/sq mi density
$137,194
Median Income
$56,020 per capita
$1,058,200
Home Value
$1,198,720 Zillow
$2,713
Median Rent
27.8% income on rent
60°F
Avg Temperature
B+
Overall
3.8 / 5.0
Good overall score based on economy, affordability, safety and education
A+
Economy
4.6 / 5.0
$137,194 median income, 5.0% unemployment
C
Affordability
2.3 / 5.0
$1,058,200 home value, $2,713/mo rent
A+
Education
4.6 / 5.0
45.3% bachelor's degree or higher
Union City enjoys a temperate climate with an average annual temperature of 60°F (16°C). Winters average 51°F in January while summers reach 66°F in July. Annual precipitation totals 16.0 inches. The area receives 0.0 inches of snow annually. Air quality is rated Good with a median AQI of 27.
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) |
Geography
| Elevation | 95 ft (29 m) |
| Area | 19.4 sq mi (50.2 km²) |
| Population Density | 3,512/sq mi |
| Coordinates | 37.6028°N, 122.0188°W |
| Timezone | America/Los_Angeles |
| County | San Mateo County County |
| Nearest Airport | Metro Oakland International (OAK) 14 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 27.0 |
| Rating | Good |
| Good Days % | 88.1% |
| Unhealthy Days | 0 |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0332 ppm |
| NO₂ (Nitrogen Dioxide) | 12.1 ppb |
| CO (Carbon Monoxide) | 0.34 ppm |
| PM2.5 (Fine Particles) | 4.5 μg/m³ |
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)
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. Sorted by wave height.
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). Sorted by distance.
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 51°F (11°C) | 2.9 in | Coldest |
| February | 54°F (12°C) | 3.1 in | |
| March | 56°F (13°C) | 2.4 in | |
| April | 58°F (15°C) | 1.2 in | |
| May | 61°F (16°C) | 0.6 in | |
| June | 65°F (18°C) | 0.2 in | |
| July | 66°F (19°C) | 0.0 in | Driest |
| August | 67°F (20°C) | 0.1 in | Warmest |
| September | 67°F (20°C) | 0.1 in | |
| October | 64°F (18°C) | 0.8 in | |
| November | 56°F (13°C) | 1.5 in | |
| December | 51°F (11°C) | 3.2 in | Wettest |
Union City has a seasonal temperature swing of 16°F / from 51°F in January to 67°F in August. Total annual precipitation is 16.0 inches, with December being the wettest month (3.2") and July the driest (0.0").