San Mateo County
California — Natural Disaster Risk Assessment
HighComposite Risk Score
National percentile: 99th
San Mateo County faces high composite natural disaster risk (NRI Risk Index score 99.2, 99th national percentile), driven primarily by earthquake and landslide exposure. Expected annual loss across all 18 hazard types is $740M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Top Hazards
All 18 Hazard Risks
| Earthquake | High | 0.14 / yr | $497M |
| Landslide | High | 3.94 / yr | $4M |
| Riverine Flood | High | 1.39 / yr | $212M |
| Drought | High | 37.99 / yr | $2M |
| Wildfire | Medium | 0.00 / yr | $2M |
| Coastal Flood | High | 0.99 / yr | $9M |
| Heat Wave | Medium | 4.46 / yr | $4M |
| Tsunami | Medium | 0.34 / yr | $7M |
| Lightning | Medium | 4.62 / yr | $549K |
| Tornado | Low | 0.05 / yr | $627K |
| Strong Wind | Low | 0.03 / yr | $222K |
| Hail | Very Low | 0.02 / yr | $43K |
| Winter Weather | Very Low | 0.61 / yr | $3K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Frequently Asked Questions
What is the overall natural disaster risk for San Mateo County?
San Mateo County has a composite FEMA National Risk Index score of 99.2 out of 100, placing it in the High category and the 99th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in San Mateo County?
The three highest-rated hazards are Earthquake (High, $497M EAL), Landslide (High, $4M EAL), Riverine Flood (High, $212M EAL). These account for most of the county's expected annual losses.
How does San Mateo County compare to other California counties?
San Mateo County ranks #12 of 58 California counties for overall natural disaster risk, with a high rating.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. San Mateo County's $740M EAL is a statistical average, not a guarantee for any specific year or address.