O'Brien County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
Very LowComposite Risk Score
National percentile: 16th
O'Brien County faces very low composite natural disaster risk (NRI Risk Index score 16.4, 16th national percentile), driven primarily by hail and drought 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 O'Brien County at very low composite risk, with a National Risk Index score of 16.4 out of 100 — placing it in the 16th 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.
Risk here concentrates in hail (ice stones from severe thunderstorms that damage property and crops) at Medium risk — $2M in expected annual loss and about 6.13 events per year; drought (extended dry periods that stress water supplies and agriculture) at Medium risk — $769K in expected annual loss and about 23.17 events per year; and winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $198K in expected annual loss and about 17.32 events per year. Across all hazards, FEMA estimates $11M in expected annual loss for a population of 14K.
Beyond physical exposure, O'Brien 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: O'Brien County has received 15 federal disaster declarations since 1965, including 6 for severe storm events and 4 for flood events. The most recent was Severe Storms, Flooding, Straight-Line Winds, and Tornadoes (severe storm), declared in June 2024.
Among 99 Iowa counties, O'Brien County ranks #91 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Hail | Medium | 6.13 / yr | $2M |
| Drought | Medium | 23.17 / yr | $769K |
| Winter Weather | Medium | 17.32 / yr | $198K |
| Tornado | Low | 0.48 / yr | $2M |
| Cold Wave | Low | 9.42 / yr | $2M |
| Ice Storm | Low | 0.86 / yr | $107K |
| Strong Wind | Low | 4.34 / yr | $511K |
| Heat Wave | Very Low | 5.16 / yr | $119K |
| Lightning | Very Low | 39.76 / yr | $112K |
| Riverine Flood | Very Low | 1.46 / yr | $4M |
| Landslide | Very Low | 0.06 / yr | $98 |
| Wildfire | Very Low | 0.00 / yr | $7K |
| Earthquake | Very Low | 0.00 / yr | $17K |
| 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
O'Brien County has received 15 federal disaster declarations since 1965, most recently Severe Storms, Flooding, Straight-Line Winds, and Tornadoes in June 2024. Most frequent causes: Severe Storm (6), Flood (4), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| June 2024 | Severe Storm | Severe Storms, Flooding, 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 |
| July 2013 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| May 2013 | Severe Storm | Severe Winter Storm |
| July 2010 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| February 2010 | Severe Storm | Severe Winter Storms and Snowstorm |
| March 2007 | Snowstorm | Snow |
Showing the 10 most recent of 15 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for O'Brien County?
O'Brien County has a composite FEMA National Risk Index score of 16.4 out of 100, placing it in the Very Low category and the 16th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in O'Brien County?
The three highest-rated hazards are Hail (Medium, $2M EAL), Drought (Medium, $769K EAL), Winter Weather (Medium, $198K EAL). These account for most of the county's expected annual losses.
How does O'Brien County compare to other Iowa counties?
O'Brien County ranks #91 of 99 Iowa counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has O'Brien County had?
FEMA records 15 federal disaster declarations for O'Brien County since 1965, most often 6 for severe storm events and 4 for flood events. The most recent was Severe Storms, Flooding, Straight-Line Winds, and Tornadoes, declared in June 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. O'Brien County's $11M EAL is a statistical average, not a guarantee for any specific year or address.