San Mateo County Disaster Risk
San Mateo County, California
FEMA Risk Rating
Relatively High
National Percentile
99th
of 3,144 counties
State Rank
#12
of 58 (1 = highest risk)
Flood Risk
98th
percentile
Hazard Risk Breakdown
Flood
River, coastal, and surface flooding risk
Relatively High
Higher than 98% of US counties
Wildfire
Wildland and wildland-urban interface fire risk
Moderate
Higher than 92% of US counties
Tornado
Tornado and severe thunderstorm risk
Very Low
Higher than 31% of US counties
Earthquake
Seismic activity and ground shaking risk
Very High
Higher than 100% of US counties
Risk Overview
About Natural Disaster Risk in San Mateo County, California
San Mateo's disaster risk ranks high nationally
San Mateo County scores 99.24 on composite risk, placing it well above the national average and earning a 'Relatively High' rating. This score reflects significant exposure to multiple hazard types, particularly earthquakes and floods that threaten the Bay Area's dense coastal communities.
Among California's riskiest counties
San Mateo's 99.24 score exceeds California's average of 88.72, ranking it in the state's upper tier for disaster vulnerability. The county faces compounded risk from its position on major fault lines and proximity to the Pacific Ocean.
Riskier than most Bay Area peers
San Mateo (99.24) faces slightly lower overall risk than neighboring Santa Clara County (99.75) but higher risk than Santa Cruz County (97.81). The three-county region represents some of California's most hazard-prone territory, driven by seismic activity and flood exposure.
Earthquakes and floods pose greatest threat
San Mateo's earthquake risk scores 99.71—among the highest in the state—while flood risk reaches 98.44, threatening low-lying areas and infrastructure. Wildfire risk (92.02) is moderate but significant, especially in the county's inland neighborhoods and open space areas.
Earthquake and flood coverage essential here
Homeowners in San Mateo should secure earthquake insurance immediately, as standard policies exclude seismic damage. Flood insurance is equally critical for residents near creeks, bays, or flood plains—especially given the county's 98.44 flood risk score.
Source: FEMA National Risk Index · Narrative reviewed by Evan Brooks, Data Editor
Preparedness Guide
What to Prepare for in San Mateo County
Top Hazards by Exposure
Source: FEMA National Risk Index v1.19.0 · Percentiles are national (3,144 counties)
Risk Advisory: San Mateo County
Risk Verdict
With a national rank of 99th percentile, San Mateo County faces above-average natural disaster pressure across several hazard categories. High composite risk signals that multiple hazard types are elevated simultaneously; planning for more than one scenario is important in San Mateo County.
Hazard Breakdown
Earthquake risk is San Mateo County's dominant natural hazard, ranked at the 100th percentile nationally under FEMA's National Risk Index. Flood ranks second at the 98th percentile nationally. Additional tracked hazards include wildfire (92th percentile), tornado (31th percentile).
Preparedness Context
San Mateo County's primary hazard, earthquake, ranks at the 100th percentile nationally. Unreinforced masonry structures carry the highest injury risk during seismic events; residents in older buildings should check with their municipality about available seismic retrofit programs. Alongside earthquake exposure, San Mateo County's flood risk at the 98th percentile nationally reinforces the value of maintaining a household emergency supply cache usable for multiple hazard scenarios. After a major earthquake, San Mateo County residents should expect water service disruption for 24 to 72 or more hours. Storing a minimum of one gallon per person per day for three days — before any event — is the most direct preparedness action households can take.
Regional Context
San Mateo County falls 10.5 points above California's typical county risk level, which means the hazard environment here is notably more demanding than the state baseline.
Is your household prepared for San Mateo County's hazards?
Review FEMA's county-specific preparedness checklists and emergency planning guides.
Frequently Asked Questions
What is the natural disaster risk in San Mateo County, CA?
What types of natural hazards affect San Mateo County?
How does San Mateo County risk compare to the California average?
Is San Mateo County at risk for earthquake?
How is natural disaster risk measured?
Why is San Mateo County higher risk than average?
Data Source
Risk data sourced from the FEMA National Risk Index (NRI). Risk scores are relative rankings (0–100) across all US counties — not absolute risk measures. Higher scores indicate higher relative risk compared to other counties.
Disclaimer: This data is informational only. It is not financial, insurance, or legal advice. Always consult a qualified professional before making insurance or real estate decisions.