Hamilton County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
LowComposite Risk Score
National percentile: 43th
Hamilton County faces low composite natural disaster risk (NRI Risk Index score 42.9, 43th national percentile), driven primarily by drought and hail exposure. Expected annual loss across all 18 hazard types is $16M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Hamilton County is low, with a National Risk Index score of 42.9 out of 100 — placing it in the 43rd national percentile and below the national average for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by drought (extended dry periods that stress water supplies and agriculture) at High risk — $4M in expected annual loss and about 11.19 events per year; hail (ice stones from severe thunderstorms that damage property and crops) at Low risk — $712K in expected annual loss and about 5.70 events per year; and strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Medium risk — $1M in expected annual loss and about 5.37 events per year. Across all hazards, FEMA estimates $16M in expected annual loss for a population of 15K.
Beyond physical exposure, Hamilton County has a low social vulnerability rating (how susceptible the population is to harm) and a 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 federal record bears this out: Hamilton County has received 21 federal disaster declarations since 1965, including 9 for severe storm events and 7 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding (severe storm), declared in May 2024.
Among 99 Iowa counties, Hamilton County ranks #35 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Drought | High | 11.19 / yr | $4M |
| Hail | Low | 5.70 / yr | $712K |
| Strong Wind | Medium | 5.37 / yr | $1M |
| Winter Weather | Medium | 16.63 / yr | $129K |
| Tornado | Low | 0.58 / yr | $2M |
| Cold Wave | Low | 9.32 / yr | $2M |
| Riverine Flood | Low | 2.18 / yr | $6M |
| Ice Storm | Low | 0.65 / yr | $58K |
| Landslide | Very Low | 0.07 / yr | $467 |
| Hurricane | Very Low | 0.01 / yr | $6K |
| Lightning | Very Low | 42.39 / yr | $69K |
| Earthquake | Very Low | 0.00 / yr | $25K |
| Wildfire | Very Low | 0.00 / yr | $5K |
| Heat Wave | Very Low | 4.16 / yr | $23K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Hamilton County has received 21 federal disaster declarations since 1965, most recently Severe Storms, Tornadoes, and Flooding in May 2024. Most frequent causes: Severe Storm (9), Flood (7), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| May 2024 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| 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 |
| August 2018 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| August 2014 | Severe Storm | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding |
| July 2010 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| May 2008 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| March 2007 | Severe Storm | Severe Winter Storms |
Showing the 10 most recent of 21 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Hamilton County?
Hamilton County has a composite FEMA National Risk Index score of 42.9 out of 100, placing it in the Low category and the 43th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Hamilton County?
The three highest-rated hazards are Drought (High, $4M EAL), Hail (Low, $712K EAL), Strong Wind (Medium, $1M EAL). These account for most of the county's expected annual losses.
How does Hamilton County compare to other Iowa counties?
Hamilton County ranks #35 of 99 Iowa counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Hamilton County had?
FEMA records 21 federal disaster declarations for Hamilton County since 1965, most often 9 for severe storm events and 7 for flood events. The most recent was Severe Storms, Tornadoes, and Flooding, 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. Hamilton County's $16M EAL is a statistical average, not a guarantee for any specific year or address.