San Mateo County, California

San Mateo County, California has a relatively high overall risk from natural hazards in FEMA's National Risk Index. Its risk score is in the top 1% of US counties. It ranks 12th of 58 counties in California. The costliest hazards here are earthquakes, inland flooding and coastal flooding. FEMA estimates about $740 million a year in expected losses, or roughly $969 per resident. Since 1977 it has been included in 22 federal disaster or emergency declarations for natural events (16 major disasters). The most recent was in April 2023 (severe winter storms, straight-line winds, flooding, landslides and mudslides). About 1 in 56 homes here carry federal flood insurance (3,346 policies). Since 1978, federal flood insurance has paid about $20 million on 1,110 claims here.

FEMA National Risk Index December 2025; OpenFEMA declarations to Nov 6, 2026; NFIP records. Updated November 6, 2026.

Scores are percentiles: a score of 90 means higher risk than about 90% of US counties for that hazard. Hazards FEMA does not rate here are left out. Social vulnerability is relatively low and community resilience is very high in FEMA's measures.

The National Weather Service has logged 164 storm reports in San Mateo County since 1958, with 3 deaths and 20 injuries and about $13.9 million in reported damage. The strongest on record here was an F1 tornado on March 20, 2005 near South San Francisco.

Source: NOAA Storm Events Database, county-based reports through Jan 5, 2026. Tornado records start in 1950, hail and wind in 1955, and floods and other storm types in 1996, so older decades undercount. Damage is in dollars of the year it happened and is often an estimate. Winter storms, heat and hurricanes are logged by forecast zone, not county, so they are not counted here.

National Flood Insurance Program (NFIP) records only; private flood policies are not included. Home counts as of Aug 3, 2026. Since 2021 NFIP prices each home separately under Risk Rating 2.0, so your price depends on the building, not the county. Ask an agent for a quote.

Older homes and mobile homes usually suffer more damage in storms, floods and earthquakes, and can cost more to insure. If you are buying, ask about roof age, foundation bolting and any retrofits. Source: US Census Bureau, American Community Survey 2020 to 2024 5-year estimates; 287,184 housing units.

Sources: FEMA National Risk Index (December 2025), OpenFEMA Disaster Declarations Summaries, and NFIP policy and claims data. Hazard Compass is independent and not affiliated with FEMA. These figures describe the whole county, not a single property, and are not insurance or safety advice. Report a problem.