Gregory County, South Dakota: Natural Disaster Risk and History
Gregory County, South Dakota has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 16.2 out of 100, higher than about 16% of US counties, with cold waves, wildfires and winter storms scoring highest of its 18 hazards and $7.5 million a year in expected losses.
OpenFEMA lists 20 federal disaster declarations that included Gregory County since 1976, not counting 2 for COVID-19; the latest is DR-4807-SD (Severe Storms, Straight-Line Winds, and Flooding, declared 15 August 2024). NOAA's Storm Prediction Center recorded 28 tornadoes touching Gregory County from 1950 to 2025.
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Population 3,989 Buildings worth $2.7 billion Area 1,064 sq mi Risk rank in South Dakota 38 of 66 FIPS 46053
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Cold wave | Relatively Moderate | 75.7 | $3.3 million | about 5.6 a year | 106 |
| Wildfire | Relatively Low | 70.0 | $208,300 | rarer than once in 1,000 years | — |
| Winter weather | Relatively Moderate | 65.3 | $130,570 | about 15 a year | 292 |
| Ice storm | Relatively Low | 57.9 | $145,566 | about once every 2.6 years | 27 |
| Drought | Relatively Low | 57.5 | $288,076 | about 26 a year | 763 |
| Hail | Relatively Low | 48.4 | $293,917 | about 4.5 a year | 170 |
| Tornado | Relatively Low | 29.0 | $575,862 | about once every 2.4 years | 23 |
| Landslide | Very Low | 20.9 | $153 | about once every 2.1 years | — |
| Strong wind | Very Low | 16.4 | $168,576 | about 2.3 a year | 86 |
| Earthquake | Very Low | 15.5 | $21,093 | rarer than once in 1,000 years | — |
| Inland flooding | Very Low | 15.4 | $2.2 million | about once every 2.2 years | 13 |
| Lightning | Very Low | 9.8 | $39,504 | about 37 a year | 43,015 strikes |
| Heat wave | Very Low | 9.3 | $18,810 | about 5.8 a year | 100 |
| Avalanche | Not Applicable | — | — | — | — |
| Coastal flooding | Not Applicable | — | — | — | — |
| Hurricane | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
| Volcanic activity | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 20
Most common: Severe Storm 9, Flood 8, Coastal Storm 1, Snowstorm 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 1 | Drought |
| 1990s | 5 | Flood ×2, Severe Storm ×2, Snowstorm |
| 2000s | 5 | Severe Storm ×3, Coastal Storm, Flood |
| 2010s | 8 | Severe Storm ×4, Flood ×4 |
| 2020s | 1 | Flood |
The last 10
Widest declarations that included Gregory County
- Hurricane Katrina Evacuation (2005, EM-3234-SD): 66 South Dakota counties designated.
- Severe Flooding, Sever Winter Storms,heavy Rains High Winds (1997, DR-1173-SD): 66 South Dakota counties designated.
- Severe Winter Storms and Blizzard Conditions (1997, DR-1156-SD): 66 South Dakota counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. South Dakota also had 18 statewide declarations with no county list.
Tornado record since 1950 28
| Tornadoes touching the county | 28 |
|---|---|
| Strongest-rated | (E)F3 ×2 |
| Peak month | June (11) |
| Deadliest | 27 May 1959, F1, 0.1 mi path, 0 killed, 3 injured |
| Longest path | 21 May 1962, F1, 47.9 mi path, 0 killed, 2 injured |
| Most recent | 28 Jul 2025, EF1, 11.7 mi path |
| Deaths / injuries on those paths | 0 / 9 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 15 | 5 | 6 | 2 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 3 | 8 | 0 | 3 | 2 | 5 | 4 | 3 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Gregory County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Gregory County (this page) | — | Very Low | 16.2 | Cold wave |
| Boyd County, NE | 47 km | Very Low | 3.4 | Drought |
| Charles Mix County | 48 km | Relatively Low | 48.5 | Cold wave |
| Keya Paha County, NE | 55 km | Very Low | 1.5 | Wildfire |
| Brule County | 59 km | Relatively Low | 58.7 | Cold wave |
| Tripp County | 59 km | Very Low | 36.5 | Cold wave |
Nearest by distance between county centres. Every county in South Dakota, ranked.
Vulnerability and resilience
| Social vulnerability | Very Low 18.9 |
|---|---|
| Community resilience | Relatively High 78.3 |
| Community risk factor | 0.87 |
| Expected annual loss, all hazards | $7.5 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Gregory County's main hazards
- Right now: National Weather Service alerts for South Dakota · all official warnings on Global Incident Tracker.
- Cold wave: Carbon monoxide in winter · Power outages now
- Wildfire: US wildfires now · Wildfire smoke: what protects you
- Winter weather: Power outages now · Carbon monoxide in winter
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Gregory County
What natural disasters is Gregory County, South Dakota most at risk from?
Gregory County, South Dakota has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 16.2 out of 100, higher than about 16% of US counties, with cold waves, wildfires and winter storms scoring highest of its 18 hazards and $7.5 million a year in expected losses.
How many federal disaster declarations has Gregory County had?
OpenFEMA lists 20 federal disaster declarations that included Gregory County since 1976, not counting 2 for COVID-19; the latest is DR-4807-SD (Severe Storms, Straight-Line Winds, and Flooding, declared 15 August 2024). Another 18 South Dakota declarations were made statewide without a county list.
How many tornadoes have hit Gregory County?
NOAA's Storm Prediction Center recorded 28 tornadoes touching Gregory County from 1950 to 2025. The deadliest: 27 May 1959, F1, 0.1 mi path, 0 killed, 3 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.