Contra Costa County, CA Environment & Hazard Risk
Very High natural hazard risk, led by earthquake. 472 storm events since 1996.
- Expected yearly loss
- $971M
- Relatively High nationally
- Storm events since 1996
- 472
- Most often strong wind
- Flood insurance policies
- 2,681
- 0.9% of homes
- Hurricanes nearby
- 0
- Since 1851
Natural hazard risk
FEMA National Risk Index, December 2025
Overall risk
Very High
Score 99.5 of 100
Social vulnerability
Relatively Low
Score 21.5 of 100
Community resilience
Relatively High
Score 67.8 of 100
Community resilience runs the other way: a higher rating means a community can recover faster.
Building value exposed: $245B · Agriculture value exposed: $107M · Risk-adjusted yearly loss: $876M
Risk by hazard
- EarthquakeRelatively High$519M/yr expected annual loss, about once every 8 years
- LandslideRelatively High$2.37M/yr expected annual loss, about 20 events a year
- Heat waveRelatively High$17.84M/yr expected annual loss, about 8.5 events a year
- WildfireRelatively Moderate$10.79M/yr expected annual loss, about once every 210 years
- DroughtRelatively High$2.85M/yr expected annual loss, about 56 events a year
- LightningRelatively High$1.46M/yr expected annual loss, about 4.5 events a year
- Volcanic activityVery Low$343/yr expected annual loss, about once every 3,333 years
- Coastal floodingRelatively Moderate$1M/yr expected annual loss, about 1.5 events a year
- TornadoRelatively Low$1.43M/yr expected annual loss, about once every 10 years
- TsunamiRelatively Low$1.03M/yr expected annual loss, about once every 3 years
- Strong windRelatively Low$398K/yr expected annual loss, about once every 25 years
- HailVery Low$157K/yr expected annual loss, about once every 23 years
- Winter weatherVery Low$8,045/yr expected annual loss, about once every 2 years
- AvalancheVery Low$3/yr expected annual loss, about once every 100 years
Bars show the national percentile score (0 to 100) for each hazard. Dollar figures are expected annual losses to buildings, people and crops. Not rated here: cold wave, hurricane, ice storm, riverine flooding.
Flood risk and insurance
National Flood Insurance Program and FEMA flood maps
Check the flood zone for an address
- Homes with flood insurance
- 2,681 of 310,943 (0.9%)
- Homes in high-risk flood zones
- 7,128
- Insured in high-risk zones
- 1,997 (28%)
- Flood claims since 1978
- 1,202
- Claims paid since 1978
- $12.91M
Flood claims paid per year
- California Atmospheric River$2.78M · 65 claims
- Flooding$1.84M · 395 claims
- Pineapple Express - Southern$762K · 105 claims
- Winter storm$58.59K · 4 claims
- February California Atmospheric River$0 · 1 claim
Storm history
Since 1996: 472 events, 15 deaths, $65.08M in damage
- Strong Wind203 · 8 deaths
- High Wind72 · 1 death
- Flood59
- Heat29 · 2 deaths
- Dense Fog19
- Debris Flow15
- Wildfire13
- Flash Flood12
- Hail12
- Dense Smoke7
Events per year
5 tornadoes on record (EF1 1, F0 4).
Most damaging storms
Since 1996, ranked by deaths, injuries and damage
- Flood01/01/2006
Countywide, Contra Costa County
$22M damage
What happened
Widespread flooding continued into early 2006 after very heavy rains through December 31st brought 3 to 4 inches in a 24 hour period. Urban flooding initiated landslides that contributed to the damage, and small streams and creeks overflowed their banks. Much of the damage was in Walnut Creek, Richmond, San Pablo, Martinez and Orinda. Included in the damages were schools, park areas and several Government Buildings.
- Flood01/01/2006
Countywide, Contra Costa County
$22M damage
What happened
Widespread county flooding occurred after 2 to 4 inches of rain fell on the area in about 24 hours. Urban flooding initiated landslides that contributed to the damage, and small streams and creeks overflowed their banks. Much of the damage was done in Walnut Creek, Richmond, San Pablo, Martinez and Orinda. Included in the damages were schools, park areas and several Government Agency structures. Approximately 165 personal assistance claims due to flooding were filed within the County. Flooding persisted into the first few days of January 2006.
- Heavy Rain04/12/2010
Walnut Creek, Contra Costa County
2 deaths, 1 injured, $10K damage
What happened
A rain-slicked road led to the crash of a car at the intersection of Mount Diablo Boulevard and Iron Horse Regional Trail in Walnut Creek. The vehicle crashed through a fence and landed upside down in the rain-swollen San Ramon Creek bypass. The driver and one other individual perished, while one occupant was rescued three miles downstream. A Contra Costa County official stated that at the time of the crash, the water would have been 2.34 feet deep and flowing at 6.4 feet per second.
- Cold/Wind Chill12/02/2022
San Francisco Bay Shoreline
2 deaths
What happened
Two deaths were reported by police. Bodies were found in a parked car in a residential neighborhood in South San Francisco just before 6 p.m. Friday. It appears they were burning charcoal or a similar substance for heat ��� which likely filled the car with carbon monoxide, poisoning them. Temperatures dropped into the upper 30s F to low 40s F earlier that morning. The ground was wet from rain that had fallen the previous day.
- Strong Wind35 kt wind03/15/2012
San Francisco Bay Shoreline
1 death, 4 injured, $12.5K damage
What happened
In the Oakland Hills at At 4:21 am a tree fell onto the southbound lanes on SR 13 south of the Park Blvd off-ramp. A Toyota Camry carrying four people hit the tree and stopped in the center median. a Ford F-150 pickup then struck the tree and went airborne, hitting and killing the 18 year old driver of the Toyota Camry. The driver of the Ford Pickup and the three other passengers of the Toyota suffered non life threatening injuries.
- Strong Wind35 kt wind03/22/2023
East Bay Interior Valleys
1 death, 1 injured, $10 damage
What happened
A tree fell onto a car on the 1000 block of Stanley Dollar Drive in Walnut Creek, occupied by two residents of a retirement home. Contra Costa Fire responded around 7 PM and found the driver injured and the passenger dead at the scene. The road was closed as firefighters worked to clear the scene.
Latest storm reports
Newest first
- Strong Wind17 kt wind06/30/2026
San Francisco Bay Shoreline
$10 damage
- Strong Wind46 kt wind05/18/2026
East Bay Hills
$10 damage
- High Wind50 kt wind05/18/2026
East Bay Hills
- High Wind55 kt wind05/18/2026
East Bay Hills
- Heat03/20/2026
East Bay Hills
- Heat03/20/2026
San Francisco Bay Shoreline
- Heat03/20/2026
San Francisco Bay Shoreline
- Heat03/20/2026
San Francisco Bay Shoreline
Drinking water
39 community water systems serve about 578,266 people. Violations since 2021.
9 systems had health-based violations, such as a contaminant over the legal limit or a missed treatment step. 16 systems had a violation of any kind still open at last report.
- Contra Costa Water DistrictServes 210,500 · Surface water · Local governmentNo health violations
- City of AntiochServes 116,781 · Surface water · Local governmentNo health violations
- BrentwoodServes 64,513 · Purchased surface water · Local governmentNo health violations
- City of PittsburgServes 62,500 · Purchased surface water · Local governmentNo health violations
- Diablo Water DistrictServes 47,158 · Purchased surface water · Local governmentNo health violations
- City of MartinezServes 31,015 · Purchased surface water · Local governmentNo health violations
- Golden State Water Company - Bay PointServes 23,765 · Purchased surface water · PrivateNo health violations
- Town of Discovery BayServes 16,790 · Groundwater · Local governmentNo health violations
Largest systems by population served. Monitoring and reporting violations mean required tests or notices were late or missing, not that the water was unsafe.
Climate
1991-2020 normals at Mt Diablo Junction, 2.3 mi from the county center
Summer highs peak around 83°F in Aug and winter lows bottom out near 41°F in Dec. About 26.1 inches of rain falls in a typical year, with 0.7 inches of snow.
| Month | High | Low | Rain | Snow |
|---|---|---|---|---|
| Jan | 54°F | 42°F | 5.06 in | 0.1 in |
| Feb | 55°F | 42°F | 4.90 in | 0.5 in |
| Mar | 58°F | 43°F | 3.69 in | 0.1 in |
| Apr | 62°F | 44°F | 1.92 in | - |
| May | 68°F | 49°F | 1.13 in | - |
| Jun | 76°F | 55°F | 0.27 in | - |
| Jul | 83°F | 62°F | 0.01 in | - |
| Aug | 83°F | 61°F | 0.03 in | - |
| Sep | 80°F | 60°F | 0.12 in | - |
| Oct | 72°F | 54°F | 1.19 in | - |
| Nov | 60°F | 46°F | 2.65 in | - |
| Dec | 53°F | 41°F | 5.08 in | - |
| Year | 58°F average | 26.1 in | 0.7 in | |
Pollution sites
3 Superfund sites and 34 toxic release facilities in Contra Costa County
Superfund sites
- Concord Naval Weapons StationFinalConcord
- United Heckathorn co.FinalRichmond
- Liquid Gold Oil Corp.DeletedRichmond
Toxic release facilities
- Chevron Products Co Richmond Refinery806,299 lbs released, Richmond
- Martinez Refining Co LLC735,066 lbs released, Martinez
- Corteva Agriscience LLC376,444 lbs released, Pittsburg
- Phillips 66 Rodeo Renewable Energy Complex307,002 lbs released, Rodeo
- Air Liquide Large Industries US LP - Rodeo Hydrogen Plant246,132 lbs released, Rodeo
- Shell Catalysts & Technologies - Pittsburg202,730 lbs released, Pittsburg
- Mecs Inc.144,915 lbs released, Martinez
- Tesoro Refining & Marketing Co LLC111,069 lbs released, Martinez
- Air Products & Chemicals Inc (Martinez-Waterfront Road)28,349 lbs released, Martinez
- Air Products West Coast Hydrogen - HP-219,013 lbs released, Martinez
Total: 3.0 million lbs in 2024, 914,221 lbs to air.
Superfund sitesToxic release facilitiesEPA inspections and enforcementAir toxics cancer risk34 historic places
Frequently asked questions
- How risky is Contra Costa County for natural disasters?
- FEMA rates Contra Costa County very high for overall natural hazard risk, with expected losses of $971M a year. The highest-rated hazards are earthquake (relatively high), landslide (relatively high), heat wave (relatively high).
- What storms are most common in Contra Costa County?
- Since 1996, NOAA recorded 472 storm events affecting Contra Costa County, most often strong wind (203), high wind (72), flood (59).
- How many tornadoes have hit Contra Costa County?
- 5 tornadoes have been recorded in Contra Costa County since 1950.
- How many homes in Contra Costa County have flood insurance?
- 2,681 residential flood insurance policies are in force in Contra Costa County, covering about 0.9% of homes. The program has paid $12.91M on 1,202 claims here since 1978.
- What is the weather like in Contra Costa County?
- At Mt Diablo Junction, average highs reach 83°F in Aug and lows fall to 41°F in Dec, with 26.1 inches of rain a year (1991-2020 normals).
Source: FEMA (National Risk Index, NFIP), NOAA (Storm Events, HURDAT2, Climate Normals), EPA · Last updated 08/01/2026 · Storm counts include events in forecast zones that touch the county. This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA.