Sioux County, Iowa Natural Disaster Risk
FEMA National Risk Index assessment · IA
LowComposite Risk Score
National percentile: 52th
Sioux County faces low composite natural disaster risk (NRI Risk Index score 52.4, 52th national percentile), driven primarily by hail and winter weather exposure. Expected annual loss across all 18 hazard types is $30M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Sioux County carries a low composite natural disaster risk, with a National Risk Index score of 52.4 out of 100 — placing it in the 52nd 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.
Most of Sioux County's expected losses come from hail (ice stones from severe thunderstorms that damage property and crops) at High risk — $6M in expected annual loss and about 6.49 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at High risk — $557K in expected annual loss and about 16.84 events per year; and tornado (violently rotating columns of air capable of catastrophic local damage) at Medium risk — $7M in expected annual loss and about 0.68 events per year. Across all hazards, FEMA estimates $30M in expected annual loss for a population of 36K.
Beyond physical exposure, Sioux 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: Sioux County has received 15 federal disaster declarations since 1965, including 6 for severe storm events and 5 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, Sioux County ranks #23 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Hail | High | 6.49 / yr | $6M |
| Winter Weather | High | 16.84 / yr | $557K |
| Tornado | Medium | 0.68 / yr | $7M |
| Ice Storm | Medium | 0.97 / yr | $421K |
| Drought | Medium | 24.38 / yr | $1M |
| Cold Wave | Low | 7.53 / yr | $3M |
| Riverine Flood | Low | 3.29 / yr | $11M |
| Strong Wind | Low | 4.39 / yr | $934K |
| Heat Wave | Low | 5.89 / yr | $412K |
| Wildfire | Very Low | 0.00 / yr | $44K |
| Landslide | Very Low | 0.08 / yr | $538 |
| Lightning | Low | 39.38 / yr | $187K |
| Earthquake | Very Low | 0.00 / yr | $46K |
| 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
Sioux 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 (5), 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 2014 | Flood | 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 |
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 Sioux County?
Sioux County has a composite FEMA National Risk Index score of 52.4 out of 100, placing it in the Low category and the 52th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Sioux County?
The three highest-rated hazards are Hail (High, $6M EAL), Winter Weather (High, $557K EAL), Tornado (Medium, $7M EAL). These account for most of the county's expected annual losses.
How does Sioux County compare to other Iowa counties?
Sioux County ranks #23 of 99 Iowa counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Sioux County had?
FEMA records 15 federal disaster declarations for Sioux County since 1965, most often 6 for severe storm events and 5 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. Sioux County's $30M EAL is a statistical average, not a guarantee for any specific year or address.