Story County, Iowa

What hazards hit Story County most?

The most frequent records are severe thunderstorm wind events: 390 since 1968. 53% of its severe thunderstorm wind events since 1968 fell in June and July. The rank column places the county among Iowa's counties by days with a record per 1,000 square miles of land over each hazard's complete period.

Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.

How many tornadoes has Story County had?

NOAA records 64 tornadoes in Story County from 1950 to 2025, the strongest rated F5, with 1 death and 21 injuries recorded in the county. That is 3rd of 99 Iowa counties and 70th of 3,080 U.S. counties by days with tornadoes per 1,000 square miles since 1950. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.

Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 66 tornadoes whose track touched Story County since 1950 (NOAA's county records number 64: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 1 person.

Map of the strongest tornado tracks in Iowa.

Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.

When was the last damaging storm in Story County?

The most recent record with damage, injuries or deaths is the May 21, 2024 tornado (2 injuries and $3.0 million in damage in 2025 dollars).

This tornado moved into Story County from Polk County. The tornado was quite wide at this point nearing 1000 yards wide at times. Along Highway 210 southeast of Cambridge, 8 large wooden and relatively new higher voltage power poles were snapped. Trees were obliterated along 315th Street east of Cambridge. Additional EF2 damage occurred 620th Avenue where numerous outbuildings were destroyed. A house was completely removed from its foundation at the intersection of 270th Street and Woods Rd and was tossed across 270th Street. However, the house was undergoing a remodel at the time and had no anchorage to the pour concrete foundation, hence the EF2 rating at this location. Damage to a house along 250th Street southeast of Nevada was extensive with the house shifted off the foundation and much of the interior savaged by flying debris and mud. …
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 1170190)

Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.

The deadliest and costliest records

Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.

Is it getting more frequent?

Records per decade for Story County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

53% of its severe thunderstorm wind events since 1968 fell in June and July. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for Story County

FEMA's register lists 22 declarations that include Story County: 20 major disasters, 2 emergencies and 0 fire management assistance declarations. Most were for severe storm (13) and flood (6).

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.

How many floods has Story County had?

NOAA's Storm Events Database holds 142 flood or flash flood records for Story County from 1996 to 2024, on 76 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Story County ranks 773rd of 2,942 U.S. counties.

The National Flood Insurance Program has paid $13.1 million on 286 claims filed in Story County; the most in one year was 78 in 2010. Claims count insured losses only: uninsured flood damage is not in this file.

Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.

FEMA's modeled risk for Story County

FEMA's National Risk Index rates Story County Relatively Low overall, with an expected annual loss of $36.1 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with Story County

1. Polk County 2,373
2. Story County 1,320
3. Boone County 806
4. Jasper County 776
5. Marshall County 748
6. Hardin County 693
7. Hamilton County 683

Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.

Next

• Tornadoes in IowaEvery Iowa tornado since 1950 and the counties with the most per square mile
• Severe thunderstorm wind in IowaThe state's severe thunderstorm wind events, by county, year and month
• The Iowa recordEvery hazard in the state, its deadliest events and its federal declarations
• FEMA's risk rating for each hazard in Story CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Story County's FEMA declarations (CSV)22 rows: every declaration that named the county, for your own analysis