Contra Costa County, California

What hazards hit Contra Costa County most?

The most frequent records are high wind and dust records: 232 since 2005. 40% of its high wind and dust records since 2005 fell in January and February. The rank column places the county among California's counties by days with a record per 1,000 square miles of land over each hazard's complete period.

Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.

How many tornadoes has Contra Costa County had?

NOAA records 5 tornadoes in Contra Costa County from 1989 to 2010, the strongest rated EF1, with 0 deaths and 0 injuries recorded in the county. That is 14th of 57 California counties by days with tornadoes per 1,000 square miles since 1950. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.

Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 5 tornadoes whose track touched Contra Costa County since 1950 (NOAA's county records number 5, the same count); along their whole tracks they killed 0 people.

Map of the strongest tornado tracks in California.

Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.

When was the last damaging storm in Contra Costa County?

The most recent record with damage, injuries or deaths is the June 29, 2026 strong wind.

Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.

The deadliest and costliest records

Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.

Is it getting more frequent?

Records per decade for Contra Costa County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).

High wind and dust storms in the 2010s: 121 records against 23 in the decade before, 121 of them forecast-zone records. Cells marked z rose mostly through zone records. The local National Weather Service office files these once per forecast zone, so a change in how it draws its zones or splits a storm into records moves this count as much as the weather does; read it beside the Contra Costa County days with a record above.

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

40% of its high wind and dust records since 2005 fell in January and February. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for Contra Costa County

FEMA's register lists 21 declarations that include Contra Costa County: 16 major disasters, 5 emergencies and 0 fire management assistance declarations. Most were for flood (8) and severe storm (6).

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.

How many floods has Contra Costa County had?

NOAA's Storm Events Database holds 74 flood or flash flood records for Contra Costa County from 1996 to 2026, on 48 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Contra Costa County ranks 286th of 2,942 U.S. counties.

The National Flood Insurance Program has paid $12.9 million on 1,202 claims filed in Contra Costa County; the most in one year was 141 in 1982. Claims count insured losses only: uninsured flood damage is not in this file.

Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.

FEMA's modeled risk for Contra Costa County

FEMA's National Risk Index rates Contra Costa County Very High overall, with an expected annual loss of $971 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with Contra Costa County

1. Sonoma County 1,017
2. Marin County 753
3. Alameda County 746
4. Sacramento County 582
5. Contra Costa County 415
6. San Joaquin County 401
7. Solano County 388
8. San Francisco County 307

Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.

Next

• Tornadoes in CaliforniaEvery California tornado since 1950 and the counties with the most per square mile
• High wind and dust storms in CaliforniaThe state's high wind and dust records, by county, year and month
• The California recordEvery hazard in the state, its deadliest events and its federal declarations
• FEMA's risk rating for each hazard in Contra Costa CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Contra Costa County's FEMA declarations (CSV)21 rows: every declaration that named the county, for your own analysis