Delaware County, Iowa

What hazards hit Delaware County most?

The most frequent records are severe thunderstorm wind events: 222 since 1955. 52% of its severe thunderstorm wind events since 1955 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 Delaware County had?

NOAA records 40 tornadoes in Delaware County from 1960 to 2026, the strongest rated F4, with 0 deaths and 20 injuries recorded in the county. That is 26th of 99 Iowa 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 45 tornadoes whose track touched Delaware County since 1950 (NOAA's county records number 40: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 0 people.

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 Delaware County?

The most recent record with damage, injuries or deaths is the July 23, 2016 tornado ($6,148 in damage in 2025 dollars).

A tornado moved east from Buchanan County and a roof of a barn was removed before lifting.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 654438)

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 Delaware 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?

52% of its severe thunderstorm wind events since 1955 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 Delaware County

FEMA's register lists 18 declarations that include Delaware County: 16 major disasters, 2 emergencies and 0 fire management assistance declarations. Most were for flood (8) and severe storm (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 Delaware County had?

NOAA's Storm Events Database holds 44 flood or flash flood records for Delaware County from 1997 to 2026, on 35 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Delaware County ranks 1286th of 2,942 U.S. counties.

The National Flood Insurance Program has paid $4.1 million on 105 claims filed in Delaware County; the most in one year was 25 in 2008. 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 Delaware County

FEMA's National Risk Index rates Delaware County Relatively Low overall, with an expected annual loss of $17.1 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 Delaware County

1. Linn County 1,436
2. Dubuque County 965
3. Buchanan County 822
4. Jones County 739
5. Clayton County 716
6. Delaware County 697
7. Fayette County 634

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