Harrison County, Iowa

What hazards hit Harrison County most?

The most frequent records are hail reports: 218 since 1964. 51% of its hail reports since 1964 fell in May and June. 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 Harrison County had?

NOAA records 34 tornadoes in Harrison County from 1967 to 2026, the strongest rated F3, with 2 deaths and 18 injuries recorded in the county. 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 35 tornadoes whose track touched Harrison County since 1950 (NOAA's county records number 34: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 7 people, 2 of them in Harrison County.

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 Harrison County?

The most recent record with damage, injuries or deaths is the May 12, 2023 flash flood ($484,000 in damage in 2025 dollars).

Forest Service reported up to two dozen culverts washed out and six county roads that were partially or fully washed out. Large trees were washed into fields and there was significant damage to farm fields in several areas in the counties. There are significant areas of crop fields that likely lost in excess of 100 tons per acre from that one heavy rain event. The county estimated the damage to be approximately $400,000-$600,000.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 1097604)

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 Harrison 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?

51% of its hail reports since 1964 fell in May and June. The two busiest months are in violet.

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

Federal disaster declarations for Harrison County

FEMA's register lists 24 declarations that include Harrison County: 21 major disasters, 3 emergencies and 0 fire management assistance declarations. Most were for severe storm (9) and flood (9).

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 Harrison County had?

NOAA's Storm Events Database holds 31 flood or flash flood records for Harrison County from 1996 to 2024, on 28 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Harrison County ranks 959th of 2,942 U.S. counties.

The National Flood Insurance Program has paid $3.4 million on 192 claims filed in Harrison County; the most in one year was 72 in 2007. 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 Harrison County

FEMA's National Risk Index rates Harrison County Very Low overall, with an expected annual loss of $9.8 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 Harrison County

1. Pottawattamie County 774
2. Washington County, NE 699
3. Harrison County 698
4. Crawford County 627
5. Shelby County 590
6. Monona County 516
7. Burt County, NE 492

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
• Hail in IowaThe state's hail reports, 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 Harrison CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Harrison County's FEMA declarations (CSV)24 rows: every declaration that named the county, for your own analysis