Photo: Denise Krebs · CC BY 2.0Alton’s building-damage rate from tornadoes is in the top 1% of U.S. census tracts
On FEMA’s National Risk Index, Alton gets a B for hazard risk: lower expected damage per building than 59% of U.S. towns. Most of that expected damage is river and rain flooding (64%), then tornadoes (26%). Flood insurance has paid 5 claims here since 2024.
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 Alton 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
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 Alton’s grade
River and rain flooding is 64% of the building damage FEMA expects in Alton, and Alton’s rate of river and rain flooding damage is lower than 57% of U.S. census tracts. Tornadoes add 26%, at a rate in the top 1% of U.S. census tracts.
B lower expected damage per building than 59% of U.S. towns (21,298).
All of Alton’s residents live in one census tract; the figures are that tract’s.
In dollars, FEMA expects about $1.3M a year in losses across Alton: $660K to buildings, the rest to people and crops.
Does Alton flood? Rarely: 5 flood claims since 2024
Every paid claim on a federal flood insurance policy in Alton, from FEMA’s records: 7.7 per 1,000 homes, more than 69% of the 13,809 U.S. towns with a flood insurance record.
- The June Midwest Flooding4 claims · $1.1M
- The Iowa Flooding1 claim · $150K
Alton isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Sioux County.4 federal disasters brought FEMA money to Alton
Disasters that paid out in Alton itself (aid to households or repair grants to the City of Alton), newest first, with that year’s flood claims.
- 2024Severe Storms, Flooding, Straight-line Winds, and Tornadoes43 households applied for aid$375K aid approved$1.6M to the City of Alton for repairs5 flood claims paid that year
- 2019Severe Storms and Flooding$21K to the City of Alton for repairs
- 2013Severe Storms, Tornadoes, and Flooding$8K to the City of Alton for repairs
- 2009Severe Winter Storms and Snowstorm$5K to the City of Alton for repairs
Sioux County has had 12 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 Alton after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Alton archive →Alton and its neighbors
Alton is 2nd of the 2 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 |
|---|---|---|---|
| Orange City | A−less damage than 79% | river and rain flooding | — |
| Alton | Bless damage than 59% | 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 Alton 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.
- 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.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Alton
Is Alton at risk for natural disasters?
On FEMA’s National Risk Index, Alton has lower expected damage per building than 59% of U.S. towns: B for hazard risk. Most of the expected damage is river and rain flooding (64%) and tornadoes (26%). 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 Alton flood?
Flood insurance has paid 5 claims in Alton since 2024, $1.3M in all, or 7.7 per 1,000 homes, more than 69% of U.S. towns with a flood insurance record. The most claims came from June Midwest Flooding (4).
Is Alton 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 Sioux County, 1.2% of all homes carry federal flood insurance.
How much is flood insurance in Alton?
FEMA’s Community Rating System list shows no discount for Alton’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 Alton?
By FEMA money that reached Alton, Severe Storms, Flooding, Straight-line Winds, and Tornadoes (2024): 43 households applied for aid, $375K approved, and $1.6M to the City of Alton for repairs. By flood claims, June Midwest Flooding: 4 paid, $1.1M.
Is Alton at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (64%), and Alton’s rate for it is lower than 57% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Alton.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Alton’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.