Sully County, South Dakota Natural Disaster Risk
FEMA National Risk Index assessment · SD
Very LowComposite Risk Score
National percentile: 6th
Sully County faces very low composite natural disaster risk (NRI Risk Index score 6.3, 6th national percentile), driven primarily by wildfire and cold wave exposure. Expected annual loss across all 18 hazard types is $5M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Sully County carries a very low composite natural disaster risk, with a National Risk Index score of 6.3 out of 100 — placing it in the 6th 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.
The county's risk is driven primarily by wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $270K in expected annual loss and about 0.00 events per year; cold wave (prolonged spells of dangerously low temperatures) at Low risk — $2M in expected annual loss and about 7.74 events per year; and winter weather (heavy snow, blizzards, and hazardous winter conditions) at Low risk — $96K in expected annual loss and about 16.53 events per year. Across all hazards, FEMA estimates $5M in expected annual loss for a population of 1K.
Beyond physical exposure, Sully County has a very 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.
History supports the rating: Sully County has received 16 federal disaster declarations since 1976, including 6 for flood events and 5 for severe storm events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 66 South Dakota counties, Sully County ranks #56 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Wildfire | Low | 0.00 / yr | $270K |
| Cold Wave | Low | 7.74 / yr | $2M |
| Winter Weather | Low | 16.53 / yr | $96K |
| Drought | Low | 36.30 / yr | $150K |
| Hail | Low | 3.29 / yr | $217K |
| Ice Storm | Very Low | 0.45 / yr | $34K |
| Tornado | Very Low | 0.33 / yr | $201K |
| Riverine Flood | Very Low | 0.50 / yr | $3M |
| Strong Wind | Very Low | 2.49 / yr | $97K |
| Heat Wave | Very Low | 3.79 / yr | $17K |
| Landslide | Very Low | 0.12 / yr | $21 |
| Earthquake | Very Low | 0.00 / yr | $10K |
| Lightning | Very Low | 32.37 / yr | $10K |
| 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
Sully County has received 16 federal disaster declarations since 1976, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Flood (6), Severe Storm (5), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| June 2019 | Flood | Severe Winter Storm, Snowstorm, and Flooding |
| February 2017 | Severe Storm | Severe Winter Storm |
| May 2011 | Flood | Flooding |
| May 2010 | Flood | Flooding |
| March 2010 | Severe Storm | Severe Winter Storm |
| September 2005 | Coastal Storm | Hurricane Katrina Evacuation |
| July 2005 | Severe Storm | Severe Storm |
| April 1997 | Flood | Severe Flooding, Sever Winter Storms,Heavy Rains High Winds |
Showing the 10 most recent of 16 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Sully County?
Sully County has a composite FEMA National Risk Index score of 6.3 out of 100, placing it in the Very Low category and the 6th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Sully County?
The three highest-rated hazards are Wildfire (Low, $270K EAL), Cold Wave (Low, $2M EAL), Winter Weather (Low, $96K EAL). These account for most of the county's expected annual losses.
How does Sully County compare to other South Dakota counties?
Sully County ranks #56 of 66 South Dakota counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Sully County had?
FEMA records 16 federal disaster declarations for Sully County since 1976, most often 6 for flood events and 5 for severe storm events. The most recent was Covid-19 Pandemic, declared in April 2020.
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. Sully County's $5M EAL is a statistical average, not a guarantee for any specific year or address.