Sioux County, North Dakota Natural Disaster Risk
FEMA National Risk Index assessment · ND
LowComposite Risk Score
National percentile: 62th
Sioux County faces low composite natural disaster risk (NRI Risk Index score 62.1, 62th national percentile), driven primarily by cold wave and winter weather exposure. Expected annual loss across all 18 hazard types is $12M.
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 62.1 out of 100 — placing it in the 62nd 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 cold wave (prolonged spells of dangerously low temperatures) at High risk — $10M in expected annual loss and about 12.95 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $123K in expected annual loss and about 19.79 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $236K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $12M in expected annual loss for a population of 4K.
Beyond physical exposure, Sioux County has a very high social vulnerability rating (how susceptible the population is to harm) and a very low community resilience rating (its capacity to prepare for and recover from disasters). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
The federal record bears this out: Sioux County has received 22 federal disaster declarations since 1969, including 9 for severe storm events and 8 for flood events. The most recent was Severe Storm, Tornadoes, and Straight-Line Winds (severe storm), declared in September 2025.
Among 53 North Dakota counties, Sioux County ranks #4 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | High | 12.95 / yr | $10M |
| Winter Weather | Medium | 19.79 / yr | $123K |
| Wildfire | Low | 0.00 / yr | $236K |
| Hail | Medium | 2.84 / yr | $422K |
| Strong Wind | Medium | 1.97 / yr | $436K |
| Ice Storm | Low | 0.94 / yr | $41K |
| Tornado | Very Low | 0.29 / yr | $201K |
| Drought | Very Low | 22.28 / yr | $5K |
| Lightning | Very Low | 31.37 / yr | $37K |
| Landslide | Very Low | 0.30 / yr | $45 |
| Heat Wave | Very Low | 1.95 / yr | $24K |
| Riverine Flood | Very Low | 0.43 / yr | $726K |
| Earthquake | Very Low | 0.00 / yr | $3K |
| 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 22 federal disaster declarations since 1969, most recently Severe Storm, Tornadoes, and Straight-Line Winds in September 2025. Most frequent causes: Severe Storm (9), Flood (8), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| September 2025 | Severe Storm | Severe Storm, Tornadoes, and Straight-Line Winds |
| September 2021 | Severe Storm | Severe Storm, Straight-Line Winds, and Flooding |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| October 2013 | Severe Storm | Severe Winter Storm |
| May 2011 | Flood | Flooding |
| April 2011 | Flood | Flooding |
| April 2010 | Severe Storm | Severe Winter Storm |
| February 2010 | Severe Storm | Severe Winter Storm |
| March 2009 | Severe Storm | Severe Storms and Flooding |
Showing the 10 most recent of 22 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 62.1 out of 100, placing it in the Low category and the 62th 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 Cold Wave (High, $10M EAL), Winter Weather (Medium, $123K EAL), Wildfire (Low, $236K EAL). These account for most of the county's expected annual losses.
How does Sioux County compare to other North Dakota counties?
Sioux County ranks #4 of 53 North Dakota counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Sioux County had?
FEMA records 22 federal disaster declarations for Sioux County since 1969, most often 9 for severe storm events and 8 for flood events. The most recent was Severe Storm, Tornadoes, and Straight-Line Winds, declared in September 2025.
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 $12M EAL is a statistical average, not a guarantee for any specific year or address.