Delaware County, Iowa: Natural Disaster Risk and History
Delaware County, Iowa has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 49.7 out of 100, higher than about 49% of US counties, with hail, drought and strong winds scoring highest of its 18 hazards and $17 million a year in expected losses.
OpenFEMA lists 16 federal disaster declarations that included Delaware County since 1968, not counting 2 for COVID-19; the latest is DR-4386-IA (Severe Storms, Tornadoes, Straight-Line Winds, and Flooding, declared 20 August 2018). NOAA's Storm Prediction Center recorded 45 tornadoes touching Delaware County from 1950 to 2025.
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Population 17,486 Buildings worth $6.2 billion Area 585 sq mi Risk rank in Iowa 26 of 99 FIPS 19055
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Hail | Relatively Moderate | 86.4 | $1.4 million | about 4.5 a year | 172 |
| Drought | Relatively Moderate | 81.0 | $1.0 million | about 11 a year | 336 |
| Strong wind | Relatively Moderate | 70.0 | $1.0 million | about 5.4 a year | 206 |
| Landslide | Relatively Low | 67.9 | $5,125 | about once every 9.0 years | — |
| Inland flooding | Relatively Low | 61.7 | $10 million | about 1.2 a year | 34 |
| Tornado | Relatively Low | 58.5 | $1.8 million | about once every 2.0 years | 40 |
| Cold wave | Relatively Low | 54.9 | $1.2 million | about 8.1 a year | 154 |
| Winter weather | Relatively Low | 42.5 | $52,609 | about 17 a year | 321 |
| Heat wave | Very Low | 34.0 | $178,923 | about 4.7 a year | 71 |
| Ice storm | Relatively Low | 28.7 | $31,060 | about once every 4.1 years | 17 |
| Lightning | Relatively Low | 28.1 | $107,371 | about 41 a year | 71,621 strikes |
| Earthquake | Very Low | 24.6 | $45,831 | rarer than once in 1,000 years | — |
| Hurricane | Very Low | 19.4 | $5,936 | about once every 115 years | 0 |
| Wildfire | Very Low | 12.4 | $4,457 | rarer than once in 1,000 years | — |
| Avalanche | Not Applicable | — | — | — | — |
| Coastal flooding | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
| Volcanic activity | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 16
Most common: Flood 8, Severe Storm 7, Hurricane 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 2 | Flood ×2 |
| 1970s | 2 | Flood ×2 |
| 1990s | 3 | Flood ×2, Severe Storm |
| 2000s | 4 | Severe Storm ×2, Hurricane, Flood |
| 2010s | 5 | Severe Storm ×4, Flood |
The last 10
Widest declarations that included Delaware County
- Hurricane Katrina Evacuation (2005, EM-3239-IA): 99 Iowa counties designated.
- Severe Storms & Flooding (1993, DR-996-IA): 99 Iowa counties designated.
- Severe Storms, Tornadoes, and Flooding (2008, DR-1763-IA): 85 Iowa counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Iowa also had 7 statewide declarations with no county list.
Tornado record since 1950 45
| Tornadoes touching the county | 45 |
|---|---|
| Strongest-rated | (E)F4 ×3 |
| Peak month | May (9) |
| Deadliest | 12 Aug 1974, F4, 5 mi path, 0 killed, 12 injured |
| Longest path | 30 Apr 1954, F4, 80.4 mi path |
| Most recent | 11 Jul 2025, EF0, 1.7 mi path |
| Deaths / injuries on those paths | 0 / 26 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 12 | 14 | 10 | 4 | 3 | 0 | 2 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 3 | 4 | 4 | 6 | 9 | 7 | 6 | 6 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Delaware County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Delaware County (this page) | — | Relatively Low | 49.7 | Hail |
| Buchanan County | 39 km | Very Low | 24.0 | Drought |
| Dubuque County | 40 km | Relatively Low | 63.6 | Hail |
| Clayton County | 42 km | Very Low | 42.2 | Landslide |
| Jones County | 43 km | Very Low | 32.7 | Drought |
| Linn County | 48 km | Relatively Moderate | 86.7 | Strong wind |
Nearest by distance between county centres. Every county in Iowa, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 32.6 |
|---|---|
| Community resilience | Very High 90.7 |
| Community risk factor | 0.99 |
| Expected annual loss, all hazards | $17 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Delaware County's main hazards
- Right now: National Weather Service alerts for Iowa · all official warnings on Global Incident Tracker.
- Hail: Weather alerts for Iowa
- Drought: Drought monitor for Iowa
- Strong wind: Power outages now
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Delaware County
What natural disasters is Delaware County, Iowa most at risk from?
Delaware County, Iowa has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 49.7 out of 100, higher than about 49% of US counties, with hail, drought and strong winds scoring highest of its 18 hazards and $17 million a year in expected losses.
How many federal disaster declarations has Delaware County had?
OpenFEMA lists 16 federal disaster declarations that included Delaware County since 1968, not counting 2 for COVID-19; the latest is DR-4386-IA (Severe Storms, Tornadoes, Straight-Line Winds, and Flooding, declared 20 August 2018). Another 7 Iowa declarations were made statewide without a county list.
How many tornadoes have hit Delaware County?
NOAA's Storm Prediction Center recorded 45 tornadoes touching Delaware County from 1950 to 2025. The deadliest: 12 Aug 1974, F4, 5 mi path, 0 killed, 12 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.