1,110 flood insurance claims·$20.1M paid·8 federal flood & hurricane disasters
Share of the whole county outline, rivers and lakes included; parts FEMA hasn’t mapped count as zero.
Shaded areas are FEMA’s mapped flood hazard zones in and around San Mateo County, California. Zoomed out they are simplified; at street level the map switches to FEMA’s exact layer. Tap anywhere to check that spot, or search an address above.
Flooding in San Mateo County is primarily characterized by standard river and surface water floods, followed by significant flash flood events and occasional coastal flooding. NOAA Storm Events Database records from the last 30 years show 63 flood events, 32 flash flood events resulting in one death, and 6 coastal flood events.
Recent impacts are illustrated by a series of storm systems that struck the Bay Area and Central Coast in December 2025, culminating on Christmas Eve and Christmas Day. These storms disrupted holiday travel, triggered two tornado warnings for the coastal regions of San Mateo and Santa Cruz counties, caused at least 300 flight delays at San Francisco International Airport, and left over 400,000 customers across the Bay Area without power.
Residents in FEMA-designated Zone A should pay the most attention, as this zone accounts for the highest volume of National Flood Insurance Program claims at 535, with an average payout of $29,006 and an average recorded water depth of 4 inches. Property owners in Zone X should also take note, where 211 claims recorded an average water depth of 24 inches and an average payout of $39,197, alongside those in shaded and unshaded Zone X variations and unknown zones.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
32% of San Mateo County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
794 NFIP claims with a recorded rated flood zone, 1978 to date. The zone is the one FEMA used to rate that policy, which may not match today’s map. Source: OpenFEMA NFIP claims.
In flood insurance claims here that reported a flood depth, the average was 7 inches.
Drawn to scale against an 80-inch door. Even a few inches soaks flooring, the bottom of the drywall and anything plugged in near the floor.
Average of the depths reported on claims (zero and implausible values left out); FEMA’s record doesn’t say exactly where each depth was measured. Source: OpenFEMA NFIP claims.
The worst year was 1998, with 236 claims and $3.8M paid, the year of Severe Winter Storms and Flooding.
Bar height is scaled by square root so ordinary years stay visible next to the worst one. NFIP claims by year of loss. Source: OpenFEMA.
52 NOAA storm reports from San Mateo County describe what happened, in the words of the forecasters who covered it. Read the California flood stories →
24 federal disaster declarations since 1977, 8 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Severe Winter Storms, Flooding, Landslides, And Mudslides | Mar 9, 2023 |
| Severe Winter Storms, Straight-line Winds, Flooding, Landslides, And Mudslides | Feb 21, 2023 |
| Severe Winter Storms, Flooding, And Mudslides | Jan 8, 2023 |
| Severe Winter Storms, Flooding, Landslides, And Mudslides | Dec 27, 2022 |
| Czu Lightning Fire Complex | Aug 20, 2020 |
| Wildfires | Aug 14, 2020 |
| Severe Winter Storms, Flooding, And Mudslides | Feb 1, 2017 |
| Severe Winter Storms, Flooding, And Mudslides | Jan 18, 2017 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
101 since 1996: 32 flash floods, 63 river or area floods and 6 coastal floods or surges.
| Event | Date | Damage |
|---|---|---|
| Flood | Dec 25, 2025 | — |
| Flood | Dec 24, 2025 | — |
| Flash Flood | Dec 24, 2025 | — |
| Flood | Dec 22, 2025 | — |
| Flood | Nov 17, 2025 | — |
| Flood | Nov 13, 2025 | — |
| Flood | Feb 13, 2025 | — |
| Flood | Feb 4, 2025 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flood · Dec 25, 2025. A series of storm systems impacted the Bay Area and Central Coast from December 19 to 25th, impacting Christmas holiday travel across the region. The most impactful systems arrived on Christmas Eve and Christmas Day. Two tornado warnings were issued for the coastal regions of San Mateo and Santa Cruz counties based off radar indicated rotation. San Francisco International Airport reported delays of at least 300 fl…
Flood · Dec 24, 2025. A series of storm systems impacted the Bay Area and Central Coast from December 19 to 25th, impacting Christmas holiday travel across the region. The most impactful systems arrived on Christmas Eve and Christmas Day. Two tornado warnings were issued for the coastal regions of San Mateo and Santa Cruz counties based off radar indicated rotation. San Francisco International Airport reported delays of at least 300 fl…
Flash Flood · Dec 24, 2025. A series of storm systems impacted the Bay Area and Central Coast from December 19 to 25th, impacting Christmas holiday travel across the region. The most impactful systems arrived on Christmas Eve and Christmas Day. Two tornado warnings were issued for the coastal regions of San Mateo and Santa Cruz counties based off radar indicated rotation. San Francisco International Airport reported delays of at least 300 fl…
Flood · Dec 22, 2025. A series of storm systems impacted the Bay Area and Central Coast from December 19 to 25th, impacting Christmas holiday travel across the region. The most impactful systems arrived on Christmas Eve and Christmas Day. Two tornado warnings were issued for the coastal regions of San Mateo and Santa Cruz counties based off radar indicated rotation. San Francisco International Airport reported delays of at least 300 fl…
National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.
Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.
If a building in San Mateo County is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
Outside those zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Since Risk Rating 2.0, NFIP premiums are set for each building, so the only reliable price is a quote: FloodSmart.gov or a local agent.