Day County, South Dakota: Natural Disaster Risk and History
Day County, South Dakota has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 27.6 out of 100, higher than about 27% of US counties, with winter storms, strong winds and wildfires scoring highest of its 18 hazards and $7.2 million a year in expected losses.
OpenFEMA lists 23 federal disaster declarations that included Day County since 1976, not counting 2 for COVID-19; the latest is DR-4938-SD (Severe Storms, Straight-Line Winds, Tornadoes, and Flooding, declared 1 September 2026). NOAA's Storm Prediction Center recorded 33 tornadoes touching Day County from 1950 to 2025.
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Population 5,449 Buildings worth $3.2 billion Area 1,102 sq mi Risk rank in South Dakota 26 of 66 FIPS 46037
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Winter weather | Relatively Moderate | 85.1 | $217,360 | about 23 a year | 429 |
| Strong wind | Relatively Moderate | 82.1 | $1.1 million | about 2.9 a year | 111 |
| Wildfire | Relatively Low | 77.9 | $259,025 | about once every 901 years | — |
| Ice storm | Relatively Moderate | 76.1 | $243,095 | about once every 2.0 years | 35 |
| Cold wave | Relatively Moderate | 76.0 | $2.2 million | about 14 a year | 268 |
| Hail | Relatively Low | 69.0 | $416,376 | about 4 a year | 151 |
| Landslide | Very Low | 42.1 | $599 | about once every 6.6 years | — |
| Tornado | Relatively Low | 40.6 | $695,065 | about once every 1.7 years | 25 |
| Heat wave | Very Low | 23.2 | $65,113 | about 2.5 a year | 38 |
| Inland flooding | Very Low | 20.0 | $1.9 million | about 1.1 a year | 31 |
| Earthquake | Very Low | 14.7 | $12,243 | rarer than once in 1,000 years | — |
| Drought | Very Low | 13.6 | $126 | about once every 9.5 years | 7 |
| Lightning | Very Low | 3.1 | $8,330 | about 33 a year | 53,377 strikes |
| 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 23
Most common: Severe Storm 11, Flood 9, Winter Storm 1, Coastal Storm 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 1 | Drought |
| 1980s | 1 | Flood |
| 1990s | 6 | Flood ×3, Severe Storm ×3 |
| 2000s | 5 | Severe Storm ×3, Coastal Storm, Flood |
| 2010s | 6 | Severe Storm ×3, Flood ×3 |
| 2020s | 4 | Severe Storm ×2, Flood, Winter Storm |
The last 10
Widest declarations that included Day 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 33
| Tornadoes touching the county | 33 |
|---|---|
| Strongest-rated | (E)F2 ×2 |
| Peak month | June (13) |
| Deadliest | 25 Jun 1973, F1, 0.1 mi path, 0 killed, 1 injured |
| Longest path | 15 Jun 1953, F2, 7.6 mi path |
| Most recent | 12 May 2022, EF1, 0.1 mi path |
| Deaths / injuries on those paths | 0 / 1 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 22 | 9 | 2 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 5 | 3 | 2 | 10 | 1 | 7 | 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 Day County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Day County (this page) | — | Very Low | 27.6 | Winter weather |
| Marshall County | 44 km | Very Low | 14.5 | Winter weather |
| Codington County | 54 km | Relatively Low | 61.8 | Ice storm |
| Clark County | 57 km | Very Low | 4.5 | Cold wave |
| Roberts County | 59 km | Very Low | 37.8 | Winter weather |
| Brown County | 63 km | Relatively Low | 73.5 | Winter weather |
Nearest by distance between county centres. Every county in South Dakota, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively High 74.7 |
|---|---|
| Community resilience | Very High 84.5 |
| Community risk factor | 1.33 |
| Expected annual loss, all hazards | $7.2 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 Day County's main hazards
- Right now: National Weather Service alerts for South Dakota · all official warnings on Global Incident Tracker.
- Winter weather: Power outages now · Carbon monoxide in winter
- Strong wind: Power outages now
- Wildfire: US wildfires now · Wildfire smoke: what protects you
- 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 Day County
What natural disasters is Day County, South Dakota most at risk from?
Day County, South Dakota has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 27.6 out of 100, higher than about 27% of US counties, with winter storms, strong winds and wildfires scoring highest of its 18 hazards and $7.2 million a year in expected losses.
How many federal disaster declarations has Day County had?
OpenFEMA lists 23 federal disaster declarations that included Day County since 1976, not counting 2 for COVID-19; the latest is DR-4938-SD (Severe Storms, Straight-Line Winds, Tornadoes, and Flooding, declared 1 September 2026). Another 18 South Dakota declarations were made statewide without a county list.
How many tornadoes have hit Day County?
NOAA's Storm Prediction Center recorded 33 tornadoes touching Day County from 1950 to 2025. The deadliest: 25 Jun 1973, F1, 0.1 mi path, 0 killed, 1 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.