Lyon County, Iowa: Natural Disaster Risk and History
Lyon County, Iowa has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 19.2 out of 100, higher than about 19% of US counties, with hail, drought and winter storms scoring highest of its 18 hazards and $11 million a year in expected losses.
OpenFEMA lists 14 federal disaster declarations that included Lyon County since 1965, not counting 2 for COVID-19; the latest is DR-4796-IA (Severe Storms, Flooding, Straight-Line Winds, and Tornadoes, declared 24 June 2024). NOAA's Storm Prediction Center recorded 43 tornadoes touching Lyon County from 1950 to 2025.
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Population 11,934 Buildings worth $4.0 billion Area 594 sq mi Risk rank in Iowa 86 of 99 FIPS 19119
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 | 89.4 | $2.5 million | about 6.1 a year | 233 |
| Drought | Relatively Moderate | 72.0 | $906,288 | about 2 a year | 637 |
| Winter weather | Relatively Moderate | 71.1 | $208,655 | about 18 a year | 350 |
| Ice storm | Relatively Moderate | 67.9 | $302,845 | about 1.2 a year | 81 |
| Tornado | Relatively Low | 45.9 | $1.7 million | about once every 2.0 years | 34 |
| Cold wave | Relatively Low | 41.8 | $1.1 million | about 8.6 a year | 163 |
| Landslide | Very Low | 33.4 | $615 | about once every 15 years | — |
| Heat wave | Very Low | 29.9 | $205,656 | about 5.1 a year | 83 |
| Wildfire | Very Low | 28.4 | $19,686 | rarer than once in 1,000 years | — |
| Inland flooding | Very Low | 19.6 | $3.7 million | about 2.4 a year | 66 |
| Strong wind | Relatively Low | 18.6 | $248,180 | about 4.2 a year | 161 |
| Lightning | Very Low | 9.2 | $46,521 | about 39 a year | 47,681 strikes |
| Earthquake | Very Low | 7.5 | $11,052 | rarer than once in 1,000 years | — |
| Avalanche | Not Applicable | — | — | — | — |
| Coastal flooding | Not Applicable | — | — | — | — |
| Hurricane | 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 14
Most common: Severe Storm 6, Flood 6, Hurricane 1, Drought 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 3 | Flood ×3 |
| 1970s | 1 | Drought |
| 1990s | 1 | Flood |
| 2000s | 2 | Severe Storm, Hurricane |
| 2010s | 6 | Severe Storm ×4, Flood ×2 |
| 2020s | 1 | Severe Storm |
The last 10
Widest declarations that included Lyon 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 43
| Tornadoes touching the county | 43 |
|---|---|
| Strongest-rated | (E)F4 ×1 |
| Peak month | June (15) |
| Deadliest | 25 Jun 2010, EF4, 13.7 mi path, 0 killed, 13 injured |
| Longest path | 6 Jul 1978, F2, 14.2 mi path |
| Most recent | 28 Jul 2025, EF1, 2.1 mi path |
| Deaths / injuries on those paths | 0 / 18 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 20 | 16 | 5 | 0 | 1 | 0 | 1 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 3 | 2 | 4 | 6 | 8 | 10 | 5 | 5 |
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 Lyon County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Lyon County (this page) | — | Very Low | 19.2 | Hail |
| Rock County, MN | 33 km | Very Low | 9.4 | Hail |
| Sioux County | 33 km | Relatively Low | 52.4 | Hail |
| Lincoln County, SD | 43 km | Relatively Low | 63.0 | Winter weather |
| Osceola County | 47 km | Very Low | 14.9 | Hail |
| Nobles County, MN | 49 km | Relatively Low | 50.2 | Hail |
Nearest by distance between county centres. Every county in Iowa, ranked.
Vulnerability and resilience
| Social vulnerability | Very Low 10.6 |
|---|---|
| Community resilience | Relatively High 79.4 |
| Community risk factor | 0.68 |
| Expected annual loss, all hazards | $11 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 Lyon 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
- Winter weather: Power outages now · Carbon monoxide in winter
- 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 Lyon County
What natural disasters is Lyon County, Iowa most at risk from?
Lyon County, Iowa has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 19.2 out of 100, higher than about 19% of US counties, with hail, drought and winter storms scoring highest of its 18 hazards and $11 million a year in expected losses.
How many federal disaster declarations has Lyon County had?
OpenFEMA lists 14 federal disaster declarations that included Lyon County since 1965, not counting 2 for COVID-19; the latest is DR-4796-IA (Severe Storms, Flooding, Straight-Line Winds, and Tornadoes, declared 24 June 2024). Another 7 Iowa declarations were made statewide without a county list.
How many tornadoes have hit Lyon County?
NOAA's Storm Prediction Center recorded 43 tornadoes touching Lyon County from 1950 to 2025. The deadliest: 25 Jun 2010, EF4, 13.7 mi path, 0 killed, 13 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.