Gregory County, South Dakota Natural Disaster Risk
FEMA National Risk Index assessment · SD
Very LowComposite Risk Score
National percentile: 16th
Gregory County faces very low composite natural disaster risk (NRI Risk Index score 16.2, 16th national percentile), driven primarily by cold wave and wildfire exposure. Expected annual loss across all 18 hazard types is $7M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Gregory County carries a very low composite natural disaster risk, with a National Risk Index score of 16.2 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.
The county's risk is driven primarily by cold wave (prolonged spells of dangerously low temperatures) at Medium risk — $3M in expected annual loss and about 5.58 events per year; wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $208K in expected annual loss and about 0.00 events per year; and winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $131K in expected annual loss and about 15.37 events per year. Across all hazards, FEMA estimates $7M in expected annual loss for a population of 4K.
Beyond physical exposure, Gregory 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: Gregory County has received 22 federal disaster declarations since 1976, including 9 for severe storm events and 8 for flood events. The most recent was Severe Storms, Straight-Line Winds, and Flooding (flood), declared in August 2024.
Among 66 South Dakota counties, Gregory County ranks #38 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | Medium | 5.58 / yr | $3M |
| Wildfire | Low | 0.00 / yr | $208K |
| Winter Weather | Medium | 15.37 / yr | $131K |
| Ice Storm | Low | 0.39 / yr | $146K |
| Drought | Low | 26.37 / yr | $288K |
| Hail | Low | 4.45 / yr | $294K |
| Tornado | Low | 0.42 / yr | $576K |
| Landslide | Very Low | 0.48 / yr | $153 |
| Strong Wind | Very Low | 2.25 / yr | $169K |
| Earthquake | Very Low | 0.00 / yr | $21K |
| Riverine Flood | Very Low | 0.46 / yr | $2M |
| Lightning | Very Low | 37.06 / yr | $40K |
| Heat Wave | Very Low | 5.84 / yr | $19K |
| 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
Gregory County has received 22 federal disaster declarations since 1976, most recently Severe Storms, Straight-Line Winds, and Flooding in August 2024. Most frequent causes: Severe Storm (9), Flood (8), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| August 2024 | Flood | Severe Storms, Straight-Line Winds, and Flooding |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| November 2019 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| October 2019 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| September 2019 | Flood | Severe Storms and Flooding |
| June 2019 | Flood | Severe Winter Storm, Snowstorm, and Flooding |
| May 2011 | Flood | Flooding |
| May 2010 | Flood | Flooding |
| March 2010 | Severe Storm | Severe Winter Storm |
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 Gregory County?
Gregory County has a composite FEMA National Risk Index score of 16.2 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 Gregory County?
The three highest-rated hazards are Cold Wave (Medium, $3M EAL), Wildfire (Low, $208K EAL), Winter Weather (Medium, $131K EAL). These account for most of the county's expected annual losses.
How does Gregory County compare to other South Dakota counties?
Gregory County ranks #38 of 66 South Dakota counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Gregory County had?
FEMA records 22 federal disaster declarations for Gregory County since 1976, most often 9 for severe storm events and 8 for flood events. The most recent was Severe Storms, Straight-Line Winds, and Flooding, declared in August 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. Gregory County's $7M EAL is a statistical average, not a guarantee for any specific year or address.