Photo: Billy Hathorn · CC BY-SA 3.0On FEMA’s figures, Thornton faces less hazard damage per building than 66% of U.S. towns, led by hail
On FEMA’s National Risk Index, Thornton gets a B+ for hazard risk: lower expected damage per building than 66% of U.S. towns, #40 of 159 in Colorado. Most of that expected damage is hail (45%), then river and rain flooding (44%). Flood insurance has paid 7 claims here since 1981.
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 stands out about Thornton’s natural hazards
From FEMA’s model and FEMA’s records, below.
What Thornton faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
Hail
River and rain flooding
Tornadoes
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 Thornton’s grade
Hail is 45% of the building damage FEMA expects in Thornton, and Thornton’s rate of hail damage is in the top 1% of U.S. census tracts. Next is river and rain flooding at 44% (lower than 86% of U.S. census tracts).
B+ #40 of 159 in Colorado; lower expected damage per building than 66% of U.S. towns (21,298).
Thornton’s residents live in 34 census tracts; FEMA’s figures are combined by where they live.
The typical Colorado town has higher expected damage than 56% of U.S. towns; within the state, Thornton has less expected damage per building than 75% of Colorado towns.
Among the 400 U.S. cities of 100,000 or more, Thornton has lower expected damage per building than 77% (#91 of 400). Because it is so big, its total expected yearly loss, $30.7M, is the 351th largest of those 400.
Does Thornton flood? Rarely: 7 flood claims since 1981
Every paid claim on a federal flood insurance policy in Thornton, from FEMA’s records: 0.1 per 1,000 homes, fewer than 99% of the 13,809 U.S. towns with a flood insurance record.
- The Late summer storms3 claims · $23K
Thornton is in FEMA’s Community Rating System (class 5) for its flood-proofing work.
Insurance rates: Adams County.4 federal disasters brought FEMA money to Thornton
Disasters that paid out in Thornton itself (aid to households or repair grants to the City of Thornton), newest first, with that year’s flood claims.
- 2015Severe Storms, Tornadoes, Flooding, Landslides, and Mudslides$5.2M to the City of Thornton for repairs2 flood claims paid that year
- 2013Severe Storms, Flooding, Landslides, and Mudslides304 households applied for aid$404K aid approved$570K to the City of Thornton for repairs3 flood claims paid that year
- 2006Snow$318K to the City of Thornton for repairs
- 2003Snow$193K to the City of Thornton for repairs
Adams County has had 8 natural disasters declared by the President since 1953, most often floods, then winter storms. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Old photos of Thornton after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Thornton archive →Thornton and its neighbors
Thornton is 4th of the 9 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 |
|---|---|---|---|
| Broomfield | Aless damage than 87% | river and rain flooding | 7 |
| Northglenn | B+less damage than 73% | hail | 2 |
| Federal Heights | B+less damage than 68% | hail | 6 |
| Thornton | B+less damage than 66% | hail | 7 |
| Westminster | B+less damage than 65% | hail | 24 |
| Todd Creek | Bless damage than 64% | river and rain flooding | — |
| Sherrelwood | Bless damage than 60% | hail | 2 |
| Commerce City | Bless damage than 57% | hail | — |
| Welby | B−less damage than 51% | hail | 2 |
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 Thornton faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Park in a garage or under cover when storms are forecast.
- Stay away from windows while it falls.
- Photograph roof and car damage for your insurer.
- 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.
- Pick your spot now: the lowest floor, an inside room, no windows.
- A watch means be ready; a warning means take cover now.
- Keep shoes and a flashlight by the bed.
- 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.
- Thornton residents get 25% off flood insurance.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Thornton
Is Thornton at risk for natural disasters?
On FEMA’s National Risk Index, Thornton has lower expected damage per building than 66% of U.S. towns: B+ for hazard risk, #40 of 159 in Colorado. Most of the expected damage is hail (45%) and river and rain flooding (44%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Thornton flood?
Flood insurance has paid 7 claims in Thornton since 1981, $34K in all, or 0.1 per 1,000 homes, fewer than 99% of U.S. towns with a flood insurance record. 1 properties have flooded more than once. The most claims came from Late summer storms (3).
Is Thornton 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 Adams County, 21% of homes in mapped flood zones carry federal flood insurance, and 0.2% of all homes do.
How much is flood insurance in Thornton?
Thornton is in FEMA’s Community Rating System (class 5), which takes 25% 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 Thornton?
By FEMA money that reached Thornton, Severe Storms, Tornadoes, Flooding, Landslides, and Mudslides (2015): $5.2M to the City of Thornton for repairs. By flood claims, Late summer storms: 3 paid, $23K.
Is Thornton at risk from hail?
It is the largest share of the building damage FEMA expects here (45%), and Thornton’s rate for it is in the top 1% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Thornton.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Thornton’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.