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Onawa, IAPhoto: Jared Winkler · CC BY-SA 4.0
B+Hazard risk
Natural hazards in Onawa · FEMA

FEMA expects less hazard damage per building in Onawa than in 70% of U.S. towns, mostly from river and rain flooding

On FEMA’s National Risk Index, Onawa gets a B+ for hazard risk: lower expected damage per building than 70% of U.S. towns, #39 of 140 in Iowa. Most of that expected damage is river and rain flooding (54%), then tornadoes (27%). FEMA’s files show no paid flood insurance claims here.

River and rain flooding 54%Tornadoes 27%Hail 9%

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

less than 70%of U.S. townsLess damageMoreExpected yearly damage per dollar of building, vs. the 21,298 U.S. towns we grade#39 of 140 in Iowa
Hazard risk
B+#39 of 140
in Iowa · lower than 70% of U.S. towns
Main hazard
River and rain flooding
54% of expected building damage
Flood claims
0
paid since 1978 · $0
Disasters paid out here
8
of 17 declared for Monona County
By hazard

What Onawa 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

54%of expected building damage
Below average · lower than 78% of U.S. census tracts
Recorded about once every 2 years in the area

Tornadoes

27%of expected building damage
Well above average · in the top 2% of U.S. census tracts

Hail

9%of expected building damage
Well above average · higher than 88% of U.S. census tracts
Recorded about 6 times a year in the area

Strong wind

6%of expected building damage
Well above average · in the top 8% of U.S. census tracts
Recorded about 4 times a year in the area
Smaller shares here
 Ice storms Earthquakes Wildfire Winter storms Lightning Heat waves top 1% Cold waves Landslides
FEMA models no building damage here
Coastal floodingHurricanesAvalanchesTsunamisVolcanic activity
People, not buildings.Counting harm to people as well as buildings, FEMA’s model puts tornadoes at 38% of Onawa’s expected losses. Tornadoes do little damage to buildings (27.3%), so they aren’t part of the grade.

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.

Flood risk changes street by street. Check a specific address on FEMA’s flood map, and ask about flood insurance before you buy.
Hazard risk grade

What’s behind Onawa’s grade

River and rain flooding is 54% of the building damage FEMA expects in Onawa, and Onawa’s rate of river and rain flooding damage is lower than 78% of U.S. census tracts. Tornadoes add 27%, at a rate in the top 2% of U.S. census tracts.

Where Onawa sits
Onawa
Least damageMiddleMost damage

B+ #39 of 140 in Iowa; lower expected damage per building than 70% of U.S. towns (21,298).

All of Onawa’s residents live in one census tract; the figures are that tract’s.

What drives the damage to buildings
River and rain flooding54%Tornadoes27%Hail9%Everything else10%

The typical Iowa town has lower expected damage than 57% of U.S. towns; within the state, Onawa has less expected damage per building than 73% of Iowa towns.

In dollars, FEMA expects about $1.3M a year in losses across Onawa: $672K to buildings, the rest to people and crops.

Shared tract.All of Onawa’s 2,906 residents (2020 census) live in one census tract. FEMA publishes its model by tract, so the rate and the hazard mix are the tract’s. The flood claims below are the town’s own.
A shared figure. The grade describes the whole tract, not each street in it, and FEMA’s model is an average year for today’s buildings, not a record: the claims below are the record.

How TownRatings grades hazard risk →

Flood insurance claims

Does Onawa flood? No paid flood claims on record

FEMA’s records show no paid flood insurance claims in Onawa. That’s not a promise: most homes don’t carry flood insurance, so small floods go unrecorded.

of all homes are insured
No community discount

Onawa isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.

Insurance rates: Monona County.
Disasters

8 federal disasters brought FEMA money to Onawa

Disasters that paid out in Onawa itself (aid to households or repair grants to the City of Onawa), newest first, with that year’s flood claims.

  1. 2025Severe Winter Storm$152K to the City of Onawa for repairs
  2. 2024Severe Storms, Flooding, Straight-line Winds, and Tornadoes8 households applied for aid$18K aid approved
  3. 2019Severe Storms and Flooding12 households applied for aid$15K aid approved
  4. 2013Severe Storms, Tornadoes, and Flooding$8K to the City of Onawa for repairs
  5. 2011Flooding27 households applied for aid$67K aid approved$38K to the City of Onawa for repairs
  6. 2008Severe Storms, Tornadoes, and Flooding4 households applied for aid$12K to the City of Onawa for repairs
Show all 8
  1. 2007Severe Storms, Flooding, and Tornadoes8 households applied for aid$1K aid approved$22K to the City of Onawa for repairs
  2. 2007Snow$6K to the City of Onawa for repairs
Disasters declared, by decade
Paid out in OnawaMonona County only

Monona County has had 17 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.

Were you here?

Old photos of Onawa after a storm or flood belong in the town’s history. Add one, or share what you remember below.

Add to the Onawa archive →
Be ready

Get ready for what Onawa faces

A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.

When the river rises
  • 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.
More from Ready.gov ↗
Tornado warnings
  • 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.
More from Ready.gov ↗
Hail
  • 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.
More from Ready.gov ↗
High winds
  • Trim dead limbs over the house and driveway.
  • Tie down trash cans and outdoor furniture.
  • Stay clear of downed lines and call the utility.
More from Ready.gov ↗
Before you buy or rent
  • 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.
When a storm is coming
Forecast and alertsWeather →911, the nearest ERSafety →

Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.

Questions about natural hazards in Onawa

Is Onawa at risk for natural disasters?

On FEMA’s National Risk Index, Onawa has lower expected damage per building than 70% of U.S. towns: B+ for hazard risk, #39 of 140 in Iowa. Most of the expected damage is river and rain flooding (54%) and tornadoes (27%). 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.

Is Onawa 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 Monona County, 0.6% of all homes carry federal flood insurance.

How much is flood insurance in Onawa?

FEMA’s Community Rating System list shows no discount for Onawa’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 Onawa?

By FEMA money that reached Onawa, Severe Winter Storm (2025): $152K to the City of Onawa for repairs.

Is Onawa at risk from river and rain flooding?

It is the largest share of the building damage FEMA expects here (54%), and Onawa’s rate for it is lower than 78% of U.S. census tracts.

Storm stories

Memories, warnings and help from neighbors in Onawa.

Town Square →
Start the conversation

Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Onawa’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.