Photo: Coolcaesar at en.wikipedia · CC BY-SA 3.0On FEMA’s figures, Los Altos faces more hazard damage per building than 95% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Los Altos gets a D for hazard risk: higher expected damage per building than 95% of U.S. towns, #553 of 847 in California. Most of that expected damage is river and rain flooding (51%), then earthquakes (49%). Flood insurance has paid 4 claims here since 1983.
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 Los Altos faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Earthquakes
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 Los Altos’ grade
River and rain flooding is 51% of the building damage FEMA expects in Los Altos, and Los Altos’ rate of river and rain flooding damage is in the top 9% of U.S. census tracts. Earthquakes add 49%, at a rate in the top 4% of U.S. census tracts.
D #553 of 847 in California; higher expected damage per building than 95% of U.S. towns (21,298).
Los Altos’ residents live in 15 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, Los Altos has more expected damage per building than 65% of California towns.
In dollars, FEMA expects about $38.6M a year in losses across Los Altos: $33.3M to buildings, the rest to people and crops.
Does Los Altos flood? Rarely: 4 flood claims since 1983
Every paid claim on a federal flood insurance policy in Los Altos, from FEMA’s records: 0.3 per 1,000 homes, fewer than 94% of the 13,809 U.S. towns with a flood insurance record.
- The Pineapple Express - Southern1 claim · $2K
Los Altos is in FEMA’s Community Rating System (class 7) for its flood-proofing work.
Insurance rates: Santa Clara County.1 federal disaster brought FEMA money to Los Altos
Disasters that paid out in Los Altos itself (aid to households or repair grants to the City of Los Altos), newest first, with that year’s flood claims.
- 2022Severe Winter Storms, Flooding, Landslides, and Mudslides4 households applied for aid$24K aid approved
Santa Clara 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 3 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in Santa Clara County, 2002–2020.
Old photos of Los Altos after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Los Altos archive →Los Altos and its neighbors
Los Altos is 6th of the 7 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 |
|---|---|---|---|
| Los Altos Hills | Dmore damage than 88% | earthquakes | 6 |
| Loyola | Dmore damage than 91% | earthquakes | — |
| Mountain View | Dmore damage than 92% | earthquakes | 5 |
| Sunnyvale | Dmore damage than 92% | earthquakes | 5 |
| Cupertino | Dmore damage than 94% | earthquakes | 10 |
| Los Altos | Dmore damage than 95% | river and rain flooding | 4 |
| Palo Alto | D−more damage than 96% | earthquakes | 376 |
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 Los Altos faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- 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.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- 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.
- Los Altos residents get 15% off flood insurance.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Los Altos
Is Los Altos at risk for natural disasters?
On FEMA’s National Risk Index, Los Altos has higher expected damage per building than 95% of U.S. towns: D for hazard risk, #553 of 847 in California. Most of the expected damage is river and rain flooding (51%) and earthquakes (49%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Los Altos flood?
Flood insurance has paid 4 claims in Los Altos since 1983, $33K in all, or 0.3 per 1,000 homes, fewer than 94% of U.S. towns with a flood insurance record. The most claims came from Pineapple Express - Southern (1).
Is Los Altos 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 Santa Clara County, 22% of homes in mapped flood zones carry federal flood insurance, and 1.7% of all homes do.
How much is flood insurance in Los Altos?
Los Altos is in FEMA’s Community Rating System (class 7), which takes 15% off federal flood insurance policies for its flood-proofing work. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in Los Altos?
By FEMA money that reached Los Altos, Severe Winter Storms, Flooding, Landslides, and Mudslides (2022): 4 households applied for aid, $24K approved. By flood claims, Pineapple Express - Southern: 1 paid, $2K.
Is Los Altos at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (51%), and Los Altos’ rate for it is in the top 9% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Los Altos.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Los Altos’ 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.