San Mateo County, California

What hazards hit San Mateo County most?

The most frequent records are high wind and dust records: 412 since 1998. 50% of its high wind and dust records since 1998 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 San Mateo County had?

NOAA records 4 tornadoes in San Mateo County from 1958 to 2005, the strongest rated F1, with 0 deaths and 0 injuries recorded in the county. That is 8th 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 4 tornadoes whose track touched San Mateo County since 1950 (NOAA's county records number 4, 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 San Mateo 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 San Mateo 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: 228 records against 53 in the decade before, 228 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 San Mateo 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?

50% of its high wind and dust records since 1998 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 San Mateo County

FEMA's register lists 24 declarations that include San Mateo County: 17 major disasters, 5 emergencies and 2 fire management assistance declarations. Most were for severe storm (7) and flood (7).

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 San Mateo County had?

NOAA's Storm Events Database holds 107 flood or flash flood records for San Mateo County from 1996 to 2026, on 59 days, with 1 death. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), San Mateo County ranks 305th of 2,942 U.S. counties.

The National Flood Insurance Program has paid $20.1 million on 1,110 claims filed in San Mateo County; the most in one year was 236 in 1998. 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 San Mateo County

FEMA's National Risk Index rates San Mateo County Relatively High overall, with an expected annual loss of $740 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 San Mateo County

1. Santa Clara County 910
2. Alameda County 746
3. San Mateo County 709
4. Santa Cruz County 681
5. 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 San Mateo CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download San Mateo County's FEMA declarations (CSV)24 rows: every declaration that named the county, for your own analysis