SkyGround

County-level natural hazard risk data for researchers

All counties

San Mateo County, CA

Population: 763,661 · FIPS code: 06081

Relatively High Overall risk index: 99.2 / 100 (percentile among US counties)

Hazard breakdown

Hazard NRI rating NRI score NOAA events
(2016–2025)
Wildfire Relatively Moderate 92 0
Inland Flooding Relatively High 98.4 53
Coastal Flooding Relatively High 91.8 0
Earthquake Relatively High 99.7 —
Heat Wave Relatively Moderate 91.6 0
Tornado Relatively Low 30.6 0

NOAA event counts are recorded county-level storm events from the NOAA Storm Events Database for 2016–2025. NOAA does not track earthquakes, and some hazard reports are filed by NWS forecast zone rather than county, so these counts are a partial, not exhaustive, record of recent activity. See the methodology page for details.

Federal disaster declaration history

San Mateo County has been included in 24 federal disaster declarations between 1977 and 2023, most recently for Flood in 2023 (SEVERE WINTER STORMS, FLOODING, AND MUDSLIDES).

Source: FEMA OpenFEMA Disaster Declarations Summaries. Counts reflect county-level declaration records (a single disaster can produce more than one record per county), not modeled risk.

Geomagnetic latitude

San Mateo County sits at approximately 43.0°N geomagnetic latitude. Aurora is rarely visible this far from the geomagnetic poles, even during the most severe (G5) geomagnetic storms — though historic extreme storms have occasionally been seen at unusually low latitudes. See current space weather conditions for live geomagnetic activity and aurora forecasts.

Geomagnetic latitude is an approximate dipole-model calculation based on this county's geographic centroid (US Census Bureau). See the methodology page for details and limitations.

What these ratings mean

Each score reflects how San Mateo County's expected losses from that hazard compare to every other county in the country, based on FEMA's National Risk Index. A "Very High" rating means this county is among the most exposed in the US for that hazard relative to other counties — it does not mean a disaster is likely this year. See the methodology page for how these scores are calculated.