San Mateo County Disaster Risk

San Mateo County has a FEMA National Risk Index rating of Relatively High, placing it in the 99th percentile nationally out of 3,144 counties. This composite score reflects the county's overall exposure to natural hazards including floods, wildfires, tornadoes, earthquakes, and hurricanes, weighted by expected annual loss and social vulnerability.

San Mateo County is evaluated for five major natural hazard types: earthquake (100th percentile), flooding (98th percentile), wildfire (92th percentile), tornado (31th percentile). The highest-risk hazard is earthquake at the 100th percentile nationally. These scores are derived from FEMA's National Risk Index, which analyzes expected annual loss, social vulnerability, and community resilience for each hazard type.

San Mateo County's composite risk percentile is 99th, compared to the California state average of 89th percentile. The state's overall risk rating is Relatively Moderate. This means San Mateo County faces higher natural disaster risk than the typical county in California.

Yes, San Mateo County's earthquake risk is at the 100th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, San Mateo County is at the 98th percentile.

FEMA's National Risk Index (NRI) calculates risk scores for 18 natural hazard types across all U.S. counties and census tracts. The composite score combines Expected Annual Loss (estimated dollar losses from each hazard), Social Vulnerability (demographic factors affecting disaster impact), and Community Resilience (ability to recover). Percentile scores rank each county against all 3,144 U.S. counties, and risk ratings range from Very Low to Very High.

San Mateo County's composite risk score of 99th percentile is above the California state average of 89th percentile. This elevated risk is driven by earthquake exposure (100th percentile), along with flooding and wildfire risk. Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.