Photo: YonderStone · CC BY-SA 4.0More hazard damage per building is expected in San Dimas than in 92% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, San Dimas gets a D for hazard risk: higher expected damage per building than 92% of U.S. towns, #381 of 847 in California. Most of that expected damage is river and rain flooding (54%), then earthquakes (43%). Flood insurance has paid 4 claims here since 1980.
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 San Dimas 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 San Dimas’ grade
River and rain flooding is 54% of the building damage FEMA expects in San Dimas, and San Dimas’ rate of river and rain flooding damage is higher than 87% of U.S. census tracts. Earthquakes add 43%, at a rate in the top 8% of U.S. census tracts.
D #381 of 847 in California; higher expected damage per building than 92% of U.S. towns (21,298).
San Dimas’ residents live in 9 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, San Dimas has less expected damage per building than 55% of California towns.
In dollars, FEMA expects about $23.5M a year in losses across San Dimas: $19.3M to buildings, the rest to people and crops.
Does San Dimas flood? Rarely: 4 flood claims since 1980
Every paid claim on a federal flood insurance policy in San Dimas, 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 - Southern2 claims · $4K
San Dimas isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Los Angeles County.3 federal disasters brought FEMA money to San Dimas
Disasters that paid out in San Dimas itself (aid to households or repair grants to the City of San Dimas), newest first, with that year’s flood claims.
- 2025Wildfires and Straight-line Winds84 households applied for aid$770 aid approved
- 2023Severe Winter Storms, Straight-line Winds, Flooding, Landslides, and Mudslides$17K to the City of San Dimas for repairs
- 2004Severe Storms, Flooding, Debris Flows, and Mudslides18 households applied for aid$5K aid approved$70K to the City of San Dimas for repairs
Los Angeles County has had 40 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 44 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in Los Angeles County, 2002–2025.
Old photos of San Dimas after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the San Dimas archive →San Dimas and its neighbors
San Dimas is 2nd 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 |
|---|---|---|---|
| Charter Oak | Dmore damage than 91% | earthquakes | — |
| San Dimas | Dmore damage than 92% | river and rain flooding | 4 |
| Covina | Dmore damage than 92% | earthquakes | 1 |
| Glendora | Dmore damage than 95% | river and rain flooding | 8 |
| La Verne | D−more damage than 95% | river and rain flooding | 2 |
| Pomona | D−more damage than 97% | river and rain flooding | 5 |
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 San Dimas 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.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in San Dimas
Is San Dimas at risk for natural disasters?
On FEMA’s National Risk Index, San Dimas has higher expected damage per building than 92% of U.S. towns: D for hazard risk, #381 of 847 in California. Most of the expected damage is river and rain flooding (54%) and earthquakes (43%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does San Dimas flood?
Flood insurance has paid 4 claims in San Dimas since 1980, $10K 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 (2).
Is San Dimas 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 Los Angeles County, 33% of homes in mapped flood zones carry federal flood insurance, and 0.5% of all homes do.
How much is flood insurance in San Dimas?
FEMA’s Community Rating System list shows no discount for San Dimas’ 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 San Dimas?
By FEMA money that reached San Dimas, Severe Storms, Flooding, Debris Flows, and Mudslides (2004): 18 households applied for aid, $5K approved, and $70K to the City of San Dimas for repairs. By flood claims, Pineapple Express - Southern: 2 paid, $4K.
Is San Dimas at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (54%), and San Dimas’ rate for it is higher than 87% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in San Dimas.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where San Dimas’ 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.