Mahaska County, Iowa

What hazards hit Mahaska County most?

The most frequent records are severe thunderstorm wind events: 151 since 1957. 48% of its severe thunderstorm wind events since 1957 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 Mahaska County had?

NOAA records 27 tornadoes in Mahaska County from 1953 to 2018, the strongest rated F4, with 1 death and 36 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 27 tornadoes whose track touched Mahaska County since 1950 (NOAA's county records number 27, the same count); along their whole tracks they killed 0 people, 1 of them in Mahaska 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 Mahaska County?

The most recent record with damage, injuries or deaths is the May 28, 2019 flood ($404,000 in damage in 2025 dollars).

The Muchakinock Creek gauge went into flood during the evening hours on the 28th and continued into the early afternoon hours of the 29th. Water goes over the road on Highway 92 west of Oskaloosa when it is flooding.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 827217)

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

A damage figure marked "step" is a record from before 1993: NOAA then filed damage by category, and the figure is the category as entered, in the dollars of that year, not an estimate of the loss.

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 Mahaska 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?

48% of its severe thunderstorm wind events since 1957 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 Mahaska County

FEMA's register lists 20 declarations that include Mahaska County: 18 major disasters, 2 emergencies and 0 fire management assistance declarations. Most were for severe storm (8) and flood (7).

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 Mahaska County had?

NOAA's Storm Events Database holds 146 flood or flash flood records for Mahaska County from 1996 to 2024, on 112 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Mahaska County ranks 2321st of 2,942 U.S. counties.

The National Flood Insurance Program has paid $134,000 on 11 claims filed in Mahaska County; the most in one year was 6 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 Mahaska County

FEMA's National Risk Index rates Mahaska County Very Low overall, with an expected annual loss of $11.1 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 Mahaska County

1. Marion County 919
2. Jasper County 776
3. Wapello County 770
4. Mahaska County 622
5. Poweshiek County 554
6. Keokuk County 482
7. Monroe County 405

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 Mahaska CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Mahaska County's FEMA declarations (CSV)20 rows: every declaration that named the county, for your own analysis