Photo: Originally uploaded by Rockero (Transferred by JaumeBG) · Public domainFEMA expects more hazard damage per building in Ontario than almost anywhere in the U.S., mostly from river and rain flooding
On FEMA’s National Risk Index, Ontario gets a D− for hazard risk: among the highest expected damage per building of U.S. towns, #762 of 847 in California. Most of that expected damage is river and rain flooding (60%), then earthquakes (37%). Flood insurance has paid 10 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 Ontario 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 Ontario’s grade
River and rain flooding is 60% of the building damage FEMA expects in Ontario, and Ontario’s rate of river and rain flooding damage is in the top 1% of U.S. census tracts. Earthquakes add 37%, at a rate in the top 6% of U.S. census tracts.
D− #762 of 847 in California; among the highest expected damage per building of U.S. towns (21,298).
Ontario’s residents live in 35 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, Ontario has more expected damage per building than 90% of California towns.
Among the 400 U.S. cities of 100,000 or more, Ontario has higher expected damage per building than 99% (#397 of 400). Because it is so big, its total expected yearly loss, $200M, is the 42th largest of those 400.
Does Ontario flood? Sometimes: 10 flood claims since 1980
Every paid claim on a federal flood insurance policy in Ontario, from FEMA’s records: 0.2 per 1,000 homes, fewer than 98% of the 13,809 U.S. towns with a flood insurance record.
Ontario 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 Bernardino County.7 federal disasters brought FEMA money to Ontario
Disasters that paid out in Ontario itself (aid to households or repair grants to the City of Ontario), newest first, with that year’s flood claims.
- 2023Severe Winter Storms, Straight-line Winds, Flooding, Landslides, and Mudslides40 households applied for aid$30K aid approved
- 2020Wildfires30 households applied for aid$10K aid approved
- 2010Severe Winter Storms, Flooding, and Debris and Mud Flows$19K to the City of Ontario for repairs
- 2010Severe Winter Storms, Flooding, and Debris and Mud Flows$44K to the City of Ontario for repairs
- 2007Wildfires, Flooding, Mud Flows, and Debris Flows11 households applied for aid$193K to the City of Ontario for repairs
- 2004Severe Storms, Flooding, Debris Flows, and Mudslides22 households applied for aid$11K aid approved$384K to the City of Ontario for repairs
Show all 7
- 2003Wildfires, Flooding, Mudflow and Debris Flow Directly Related T92 households applied for aid$14K aid approved
San Bernardino County has had 34 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 24 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in San Bernardino County, 2002–2024.
Old photos of Ontario after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Ontario archive →Ontario and its neighbors
Ontario 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 |
|---|---|---|---|
| Fontana | D−more damage than 96% | river and rain flooding | 7 |
| Upland | D−more damage than 98% | river and rain flooding | 10 |
| Rancho Cucamonga | D−more damage than 98% | river and rain flooding | 25 |
| Ontario | D−among the highest damage | river and rain flooding | 10 |
| Chino | D−among the highest damage | river and rain flooding | 2 |
| Eastvale | D−among the highest damage | river and rain flooding | 1 |
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 Ontario 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 Ontario
Is Ontario at risk for natural disasters?
On FEMA’s National Risk Index, Ontario has among the highest expected damage per building of U.S. towns: D− for hazard risk, #762 of 847 in California. Most of the expected damage is river and rain flooding (60%) and earthquakes (37%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Ontario flood?
Flood insurance has paid 10 claims in Ontario since 1980, $74K in all, or 0.2 per 1,000 homes, fewer than 98% of U.S. towns with a flood insurance record. 1 properties have flooded more than once.
Is Ontario 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 Bernardino County, 15% of homes in mapped flood zones carry federal flood insurance, and 0.3% of all homes do.
How much is flood insurance in Ontario?
FEMA’s Community Rating System list shows no discount for Ontario’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 Ontario?
By FEMA money that reached Ontario, Severe Storms, Flooding, Debris Flows, and Mudslides (2004): 22 households applied for aid, $11K approved, and $384K to the City of Ontario for repairs.
Is Ontario at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (60%), and Ontario’s rate for it is in the top 1% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Ontario.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Ontario’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.