San Mateo County, CA
FEMA National Risk Index scores, disaster declarations & hazard data
San Mateo County has experienced 24 federally declared disasters since 1977, most recently Severe Winter Storms, Flooding, And Mudslides in 2023. Its overall natural hazard risk is rated Relatively High — higher risk than most US counties.
San Mateo County's highest-rated hazards are earthquake, landslide, and inland flooding, with its top risk rated "Relatively High" by FEMA's National Risk Index. Recorded storm events have decreased 57% over the past five years compared to the prior five-year period. Community vulnerability is relatively low (29th percentile nationally), indicating stronger recovery capacity than most US counties.
Past disasters & FEMA designations
A federal disaster declaration officially designates a county for FEMA disaster assistance. San Mateo County has been designated in 24 declarations since 1977, covering 9 disaster types including severe storm (7), flood (7), fire (3).
| Year | Type | Event name |
|---|---|---|
| 2023 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, And Mudslides |
| 2023 | Flood | Severe Winter Storms, Flooding, Landslides, And Mudslides |
| 2023 | Flood | Severe Winter Storms, Flooding, Landslides, And Mudslides |
| 2023 | Flood | Severe Winter Storms, Flooding, And Mudslides |
| 2020 | Fire | Wildfires |
| 2020 | Fire | Czu Lightning Fire Complex |
| 2020 | Biological | Covid-19 Pandemic |
| 2020 | Biological | Covid-19 |
| 2017 | Flood | Severe Winter Storms, Flooding, And Mudslides |
| 2017 | Flood | Severe Winter Storms, Flooding, And Mudslides |
Showing the 10 most recent of 24 total declarations since 1977.
Source: FEMA OpenFEMA Disaster Declarations Summaries. A single disaster can produce more than one record per county. Data current through September 2026.
Risk by hazard type
| Hazard | Risk rating | Risk score | Recorded events | Deaths | Prop. damage |
|---|---|---|---|---|---|
| Wildfire | Relatively Moderate | 92 | 0 | 0 | — |
| Inland Flooding | Relatively High | 98.4 | 55 | 0 | $10 |
| Coastal Flooding | Relatively High | 91.8 | 1 | 0 | — |
| Earthquake | Relatively High | 99.7 | 20 | — | — |
| Heat Wave | Relatively Moderate | 91.6 | 3 | 3 | — |
| Tornado | Relatively Low | 30.6 | 0 | 0 | — |
| Hurricane | Not Applicable | — | 0 | 0 | — |
| Hail | Very Low | 11.4 | 9 | 0 | $30 |
| Strong Wind | Relatively Low | 20.6 | 0 | 0 | — |
| Winter Weather | Very Low | 3.4 | 0 | 0 | — |
| Ice Storm | Not Applicable | — | — | — | — |
| Cold Wave | No Rating | 0 | — | — | — |
| Lightning | Relatively Moderate | 68.2 | 4 | 0 | — |
| Drought | Relatively High | 92.1 | 0 | 0 | — |
| Landslide | Relatively High | 99.7 | 18 | 0 | — |
| Avalanche | Not Applicable | — | — | — | — |
| Tsunami | Relatively Moderate | 70.8 | — | — | — |
| Volcanic Activity | Not Applicable | — | — | — | — |
Scores are 0–100 percentiles relative to all US counties — higher means more exposed, not that a disaster is likely this year. Event counts: NOAA Storm Events 2016–2026; earthquake counts from USGS ComCat (M3.0+, 1996–2026). See the methodology page for details.
Community vulnerability
San Mateo County ranks in the 29th percentile (Low) for community vulnerability — a measure of how hard disaster impacts tend to hit residents. Higher vulnerability means more displacement, worse health outcomes, and slower recovery after a disaster.
| SVI theme | Percentile | Vulnerability level |
|---|---|---|
| Overall | 29th | Low |
| Socioeconomic status | 13th | Very low |
| Household characteristics | 7th | Very low |
| Racial & ethnic minority status | 94th | High |
| Housing type & transportation | 71st | Moderate |
Source: CDC/ATSDR Social Vulnerability Index 2022. Percentiles compare counties nationally — higher means more vulnerable relative to other counties. See CDC SVI for full methodology.
Future risk outlook
| Wildfire metric | National percentile | Level |
|---|---|---|
| Burn probability | 73rd | Relatively High |
| Risk to homes | 72nd | Relatively High |
| Buildings in direct exposure zone | 12.7% | — |
NOAA tracked 87 weather events in this county over 2016–2025: 61 in 2016–20 vs 26 in 2021–25 (-57% — frequency decreasing).
Wildfire: USDA Forest Service Wildfire Risk to Communities (RDS-2020-0016-2) — modeled values, not annual forecasts. See wildfirerisk.org. Inland flood and heat projections pending data availability; coastal sea-level projections are available for select coastal counties below — see the data page.
Nearby counties
Frequently asked questions
What natural hazards pose the greatest risk in San Mateo County?
According to the FEMA National Risk Index, the highest-risk hazards in San Mateo County, California are earthquake, landslide, and inland flooding. The county's overall natural hazard risk is rated Relatively High — higher risk than most US counties.
Has San Mateo County received federal disaster declarations?
Yes. San Mateo County has received 24 federal disaster declarations since 1977, including declarations in 2023. The most common disaster type on record is severe storm (7 declarations).
Has San Mateo County had any FEMA disaster declarations in 2024, 2025, or 2026?
No federal disaster declarations have been recorded for San Mateo County since the start of 2024. Its most recent declaration on record is Severe Winter Storms, Flooding, And Mudslides in 2023.
How does San Mateo County's natural hazard risk compare to nearby counties?
Among neighboring counties, Alameda County, CA has the highest overall natural hazard risk (Very High) and Marin County, CA has the lowest (Relatively High). San Mateo County is rated Relatively High overall.
How is San Mateo County's composite disaster risk index calculated?
San Mateo County's composite disaster risk index — officially FEMA's National Risk Index (NRI) — scores every US county on a 0–100 percentile scale across 18 natural hazard types, factoring in expected annual loss, social vulnerability, and community resilience. San Mateo County's composite score of 99 means its overall natural hazard risk is higher than 99% of US counties.