On FEMA’s figures, Thornton faces more hazard damage per building than 91% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Thornton gets a D for hazard risk: higher expected damage per building than 91% of U.S. towns. Most of that expected damage is river and rain flooding (95%). Flood insurance has paid 31 claims here since 1979.
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 Thornton 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
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
River and rain flooding is 95% of the building damage FEMA expects in Thornton, and Thornton’s rate of river and rain flooding damage is in the top 3% of U.S. census tracts.
D #125 of 126 in New Hampshire; higher expected damage per building than 91% of U.S. towns (21,298).
All of Thornton’s residents live in one census tract; the figures are that tract’s.
The typical New Hampshire town has higher expected damage than 58% of U.S. towns; within the state, Thornton has more expected damage per building than 99% of New Hampshire towns.
In dollars, FEMA expects about $1.7M a year in losses across Thornton: $1.5M to buildings, the rest to people and crops.
Does Thornton flood? Sometimes: 31 flood claims since 1979
Every paid claim on a federal flood insurance policy in Thornton, from FEMA’s records: 14.6 per 1,000 homes, more than 80% of the 13,809 U.S. towns with a flood insurance record.
- Hurricane Irene14 claims · $366K
- The December nor’easter1 claim · $52K
Thornton isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Grafton County.11 federal disasters brought FEMA money to Thornton
Disasters that paid out in Thornton itself (aid to households or repair grants to the Town of Thornton), newest first, with that year’s flood claims.
- 2023Severe Storm and Flooding$43K to the Town of Thornton for repairs1 flood claim paid that year
- 2022Severe Storm and Flooding$61K to the Town of Thornton for repairs
- 2017Severe Storm and Flooding$120K to the Town of Thornton for repairs
- 2017Severe Storms and Flooding$151K to the Town of Thornton for repairs
- 2012Hurricane Sandy$4K to the Town of Thornton for repairs
- 2011Tropical Storm Irene25 households applied for aid$32K aid approved$16K to the Town of Thornton for repairs14 flood claims paid for it, $366K
Show all 11
- 2008Severe Storms and Flooding$21K to the Town of Thornton for repairs
- 2007Severe Storms and Flooding5 households applied for aid$3K aid approved$39K to the Town of Thornton for repairs
- 2005Record Snow$12K to the Town of Thornton for repairs
- 2005Record And/or Near Record Snow$4K to the Town of Thornton for repairs
- 2001Snow$7K to the Town of Thornton for repairs
Grafton 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.
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 2nd of the 3 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 |
|---|---|---|---|
| Campton | Dmore damage than 91% | river and rain flooding | 26 |
| Thornton | Dmore damage than 91% | river and rain flooding | 31 |
| Woodstock | Dmore damage than 95% | river and rain flooding | 8 |
| Waterville Valley | — | 290 residents; we grade 1,000+ | |
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.
- 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 Thornton
Is Thornton at risk for natural disasters?
On FEMA’s National Risk Index, Thornton has higher expected damage per building than 91% of U.S. towns: D for hazard risk. Most of the expected damage is river and rain flooding (95%). The figures are for the one census tract the town shares with its neighbors. This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Thornton flood?
Flood insurance has paid 31 claims in Thornton since 1979, $694K in all, or 14.6 per 1,000 homes, more than 80% of U.S. towns with a flood insurance record. 5 properties have flooded more than once. The most claims came from Hurricane Irene (14).
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 Grafton County, 18% of homes in mapped flood zones carry federal flood insurance, and 1.1% of all homes do.
How much is flood insurance in Thornton?
FEMA’s Community Rating System list shows no discount for Thornton’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 Thornton?
By FEMA money that reached Thornton, Severe Storms and Flooding (2017): $151K to the Town of Thornton for repairs. By flood claims, Hurricane Irene: 14 paid, $366K.
Is Thornton at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (95%), and Thornton’s rate for it is in the top 3% 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.