Holbrook-Palmer Estate, "Elmwood" · Photo: LPS.1 · CC0On FEMA’s figures, Atherton faces more hazard damage per building than 95% of U.S. towns, mostly from earthquakes
On FEMA’s National Risk Index, Atherton gets a D for hazard risk: higher expected damage per building than 95% of U.S. towns, #527 of 847 in California. Most of that expected damage is earthquakes (52%), then river and rain flooding (48%). Flood insurance has paid 8 claims here since 1982.
Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded
What Atherton faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
Earthquakes
River and rain flooding
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
What’s behind Atherton’s grade
Earthquakes are 52% of the building damage FEMA expects in Atherton, and Atherton’s rate of earthquakes damage is in the top 4% of U.S. census tracts. Next is river and rain flooding at 48% (higher than 89% of U.S. census tracts).
D #527 of 847 in California; higher expected damage per building than 95% of U.S. towns (21,298).
Atherton’s residents live in 2 census tracts; FEMA’s figures are combined by where they live.
The typical California town has higher expected damage than 92% of U.S. towns; within the state, Atherton has more expected damage per building than 62% of California towns.
In dollars, FEMA expects about $15.0M a year in losses across Atherton: $13.1M to buildings, the rest to people and crops.
Does Atherton flood? Rarely: 8 flood claims since 1982
Every paid claim on a federal flood insurance policy in Atherton, from FEMA’s records: 3.0 per 1,000 homes, fewer than 52% of the 13,809 U.S. towns with a flood insurance record.
- The Pineapple Express - Southern5 claims · $235K
- The Winter storm1 claim · $5K
- The California Atmospheric River1 claim · $143K
Atherton isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: San Mateo County.2 federal disasters brought FEMA money to Atherton
Disasters that paid out in Atherton itself (aid to households or repair grants to the Town of Atherton), newest first, with that year’s flood claims.
- 2022Severe Winter Storms, Flooding, Landslides, and Mudslides11 households applied for aid$15K aid approved$86K to the Town of Atherton for repairs1 flood claim paid that year
- 2020Wildfires29 households applied for aid$8K aid approved
San Mateo County has had 19 natural disasters declared by the President since 1953, most often severe storms, then floods. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Also 2 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in San Mateo County, 2010–2020.
Old photos of Atherton after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Atherton archive →Atherton and its neighbors
Atherton is 4th of the 6 graded towns here, from least expected damage per building to most. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| West Menlo Park | Dmore damage than 93% | earthquakes | 4 |
| Woodside | Dmore damage than 94% | earthquakes | 10 |
| Menlo Park | Dmore damage than 94% | earthquakes | 16 |
| Atherton | Dmore damage than 95% | earthquakes | 8 |
| North Fair Oaks | Dmore damage than 95% | earthquakes | 10 |
| Redwood City | Dmore damage than 95% | earthquakes | 62 |
Hazard risk = FEMA’s expected yearly building damage per dollar of building value, vs. the 21,298 U.S. towns we grade; the map is shaded by fifths of the same scale. Flood claims = paid federal flood insurance claims on record.
Get ready for what Atherton faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Atherton
Is Atherton at risk for natural disasters?
On FEMA’s National Risk Index, Atherton has higher expected damage per building than 95% of U.S. towns: D for hazard risk, #527 of 847 in California. Most of the expected damage is earthquakes (52%) and river and rain flooding (48%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Atherton flood?
Flood insurance has paid 8 claims in Atherton since 1982, $388K in all, or 3.0 per 1,000 homes, fewer than 52% of U.S. towns with a flood insurance record. The most claims came from Pineapple Express - Southern (5).
Is Atherton in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In San Mateo County, 31% of homes in mapped flood zones carry federal flood insurance, and 1.8% of all homes do.
How much is flood insurance in Atherton?
FEMA’s Community Rating System list shows no discount for Atherton’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in Atherton?
By FEMA money that reached Atherton, Severe Winter Storms, Flooding, Landslides, and Mudslides (2022): 11 households applied for aid, $15K approved, and $86K to the Town of Atherton for repairs. By flood claims, Pineapple Express - Southern: 5 paid, $235K.
Is Atherton at risk from earthquakes?
It is the largest share of the building damage FEMA expects here (52%), and Atherton’s rate for it is in the top 4% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Atherton.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Atherton’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.