Port Costa, CA
Full City Profile · California · Marin County County
2.5
/5.0
C+
Fair
194
Population
1,213/sq mi density
$586,500
Home Value
$664,856 Zillow
62°F
Avg Temperature
C+
Overall
2.5 / 5.0
Fair overall score based on economy, affordability, safety and education
C+
Education
2.5 / 5.0
19.1% bachelor's degree or higher
Port Costa enjoys a temperate climate with an average annual temperature of 62°F (17°C). Winters average 49°F in January while summers reach 73°F in July. Annual precipitation totals 16.1 inches. The area receives 0.0 inches of snow annually. Air quality is rated Good with a median AQI of 28.
Temperature
49°F Jan (10°C)
73°F Jul (23°C)
| Annual Average | 62.0°F |
| 15% above US avg | |
| January Average | 49°F (10°C) |
| July Average | 73°F (23°C) |
Geography
| Elevation | 171 ft (52 m) |
| Area | 0.2 sq mi (0.4 km²) |
| Population Density | 1,213/sq mi |
| Coordinates | 38.0445°N, 122.1849°W |
| Timezone | America/Los_Angeles |
| County | Marin County County |
| Nearest Airport | Metro Oakland International (OAK) 22 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 28.0 |
| Rating | Good |
| Good Days % | 86.3% |
| Unhealthy Days | 0 |
Air Pollutants (EPA 2023)
| Ozone (O₃) | 0.0326 ppm |
| NO₂ (Nitrogen Dioxide) | 9.1 ppb |
| CO (Carbon Monoxide) | 0.31 ppm |
| PM2.5 (Fine Particles) | 5.4 μg/m³ |
Natural Hazard Risk
| Overall Risk | Relatively High |
| Risk Score | 96.4 / 100 |
| Social Vulnerability | 24.7 / 100 |
| Community Resilience | 99.2 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Relatively High |
| Wildfire | Relatively Moderate |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Relatively Low |
| Winter Weather | Very Low |
| Lightning | Relatively Low |
| Drought | Relatively Low |
| Cold Wave | No Rating |
| Landslide | Relatively High |
| Coastal Flood | Very High |
| Tsunami | Relatively Moderate |
| Volcano | Very Low |
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 | 39 km |
| 1989 | N. CALIFORNIA | Earthquake | 1.0 m | 62 | 115 km |
| 1856 | N. CALIFORNIA | Eruption + Earthquake | 0.6 m | - | 61 km |
| 1906 | N. CALIFORNIA | Eruption + Earthquake | 0.1 m | - | 47 km |
| 1865 | N. CALIFORNIA | Eruption + Earthquake | - | - | 97 km |
Source: NOAA/NCEI Historical Tsunami Database. Sorted by wave height.
Nearby Volcanoes
1 volcano within 200 km. Closest: Clear Lake (115 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Clear Lake | Volcanic field | 1,439 m (4,721 ft) | Unknown | 115 km |
Source: Smithsonian Institution Global Volcanism Program (GVP). Sorted by distance.
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 49°F (10°C) | 3.2 in | Coldest, Wettest |
| February | 53°F (12°C) | 3.2 in | |
| March | 57°F (14°C) | 2.3 in | |
| April | 60°F (16°C) | 1.1 in | |
| May | 65°F (19°C) | 0.5 in | |
| June | 71°F (21°C) | 0.2 in | |
| July | 73°F (23°C) | 0.0 in | Driest |
| August | 74°F (23°C) | 0.0 in | Warmest |
| September | 72°F (22°C) | 0.1 in | |
| October | 65°F (19°C) | 0.7 in | |
| November | 56°F (13°C) | 1.6 in | |
| December | 50°F (10°C) | 3.2 in |
Port Costa has a seasonal temperature swing of 24°F / from 49°F in January to 74°F in August. Total annual precipitation is 16.1 inches, with January being the wettest month (3.2") and July the driest (0.0").