Mills County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
Very LowComposite Risk Score
National percentile: 18th
Mills County faces very low composite natural disaster risk (NRI Risk Index score 18.5, 18th national percentile), driven primarily by landslide and hail exposure. Expected annual loss across all 18 hazard types is $11M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Mills County at very low composite risk, with a National Risk Index score of 18.5 out of 100 — placing it in the 18th national percentile and among the lowest-risk counties in the country. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Mills County's expected losses come from landslide (downhill movement of rock, soil, and debris on unstable slopes) at Low risk — $20K in expected annual loss and about 0.20 events per year; hail (ice stones from severe thunderstorms that damage property and crops) at Low risk — $973K in expected annual loss and about 6.83 events per year; and drought (extended dry periods that stress water supplies and agriculture) at Medium risk — $614K in expected annual loss and about 10.77 events per year. Across all hazards, FEMA estimates $11M in expected annual loss for a population of 14K.
Beyond physical exposure, Mills County has a very low social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The county's disaster history tells the same story: Mills County has received 20 federal disaster declarations since 1965, including 7 for severe storm events and 7 for flood events. The most recent was Severe Storms and Tornadoes (tornado), declared in May 2024.
Among 99 Iowa counties, Mills County ranks #87 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | Low | 0.20 / yr | $20K |
| Hail | Low | 6.83 / yr | $973K |
| Drought | Medium | 10.77 / yr | $614K |
| Tornado | Low | 0.38 / yr | $2M |
| Wildfire | Very Low | 0.00 / yr | $83K |
| Ice Storm | Low | 0.88 / yr | $83K |
| Heat Wave | Low | 8.21 / yr | $356K |
| Strong Wind | Low | 4.37 / yr | $535K |
| Winter Weather | Low | 12.89 / yr | $54K |
| Cold Wave | Low | 4.42 / yr | $592K |
| Riverine Flood | Very Low | 0.96 / yr | $5M |
| Lightning | Very Low | 46.61 / yr | $73K |
| Earthquake | Very Low | 0.00 / yr | $13K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Mills County has received 20 federal disaster declarations since 1965, most recently Severe Storms and Tornadoes in May 2024. Most frequent causes: Severe Storm (7), Flood (7), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| May 2024 | Tornado | Severe Storms and Tornadoes |
| February 2022 | Severe Storm | Severe Storms, Straight-Line Winds, and Tornadoes |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2019 | Flood | Severe Storms and Flooding |
| July 2014 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| June 2011 | Flood | Flooding |
| July 2010 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| May 2008 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| May 2007 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
Showing the 10 most recent of 20 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Mills County?
Mills County has a composite FEMA National Risk Index score of 18.5 out of 100, placing it in the Very Low category and the 18th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Mills County?
The three highest-rated hazards are Landslide (Low, $20K EAL), Hail (Low, $973K EAL), Drought (Medium, $614K EAL). These account for most of the county's expected annual losses.
How does Mills County compare to other Iowa counties?
Mills County ranks #87 of 99 Iowa counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Mills County had?
FEMA records 20 federal disaster declarations for Mills County since 1965, most often 7 for severe storm events and 7 for flood events. The most recent was Severe Storms and Tornadoes, declared in May 2024.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Mills County's $11M EAL is a statistical average, not a guarantee for any specific year or address.