Photo: Iowahwyman · CC BY-SA 3.0FEMA puts Johnston’s expected hazard damage per building below that of 86% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Johnston gets an A for hazard risk: lower expected damage per building than 86% of U.S. towns, #10 of 140 in Iowa. Most of that expected damage is river and rain flooding (64%), then tornadoes (22%). Flood insurance has paid 15 claims here since 1993.
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 Johnston 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
Strong wind
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 Johnston’s grade
River and rain flooding is 64% of the building damage FEMA expects in Johnston, and Johnston’s rate of river and rain flooding damage is lower than 80% of U.S. census tracts. Tornadoes add 22%, at a rate in the top 9% of U.S. census tracts.
A #10 of 140 in Iowa; lower expected damage per building than 86% of U.S. towns (21,298).
Johnston’s residents live in 7 census tracts; FEMA’s figures are combined by where they live.
The typical Iowa town has lower expected damage than 57% of U.S. towns; within the state, Johnston has less expected damage per building than 94% of Iowa towns.
In dollars, FEMA expects about $6.5M a year in losses across Johnston: $4.2M to buildings, the rest to people and crops.
Does Johnston flood? Sometimes: 15 flood claims since 1993
Every paid claim on a federal flood insurance policy in Johnston, from FEMA’s records: 1.5 per 1,000 homes, fewer than 68% of the 13,809 U.S. towns with a flood insurance record.
- The Storm4 claims · $344K
- The Midwest Flooding1 claim · $3K
Johnston isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Polk County.7 federal disasters brought FEMA money to Johnston
Disasters that paid out in Johnston itself (aid to households or repair grants to the City of Johnston), newest first, with that year’s flood claims.
- 2024Severe Storms, Tornadoes, and Flooding40 households applied for aid$18K aid approved$228K to the City of Johnston for repairs
- 2020Severe Storms43 households applied for aid$65K aid approved$145K to the City of Johnston for repairs
- 2018Severe Storms, Tornadoes, Straight-line Winds, and Flooding$208K to the City of Johnston for repairs2 flood claims paid that year
- 2010Severe Storms, Flooding, and Tornadoes60 households applied for aid$110K aid approved$332K to the City of Johnston for repairs3 flood claims paid that year
- 2008Severe Storms, Tornadoes, and Flooding19 households applied for aid$19K aid approved$178K to the City of Johnston for repairs8 flood claims paid that year
- 2007Severe Winter Storms$37K to the City of Johnston for repairs
Show all 7
- 2004Severe Storms, Tornadoes, and Flooding2 households applied for aid$8K aid approved$30K to the City of Johnston for repairs
Polk County has had 18 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 Johnston after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Johnston archive →Johnston and its neighbors
Johnston has the lowest expected damage per building of the 3 graded towns here. Tap a town to see its hazards.
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 Johnston 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.
- Trim dead limbs over the house and driveway.
- Tie down trash cans and outdoor furniture.
- Stay clear of downed lines and call the utility.
- 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 Johnston
Is Johnston at risk for natural disasters?
On FEMA’s National Risk Index, Johnston has lower expected damage per building than 86% of U.S. towns: A for hazard risk, #10 of 140 in Iowa. Most of the expected damage is river and rain flooding (64%) and tornadoes (22%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Johnston flood?
Flood insurance has paid 15 claims in Johnston since 1993, $930K in all, or 1.5 per 1,000 homes, fewer than 68% of U.S. towns with a flood insurance record. 3 properties have flooded more than once. The most claims came from Storm (4).
Is Johnston 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 Polk County, 23% of homes in mapped flood zones carry federal flood insurance, and 0.4% of all homes do.
How much is flood insurance in Johnston?
FEMA’s Community Rating System list shows no discount for Johnston’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 Johnston?
By FEMA money that reached Johnston, Severe Storms, Flooding, and Tornadoes (2010): 60 households applied for aid, $110K approved, and $332K to the City of Johnston for repairs. By flood claims, Storm: 4 paid, $344K.
Is Johnston at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (64%), and Johnston’s rate for it is lower than 80% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Johnston.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Johnston’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.