States › South Dakota › Dewey County
Dewey County, South Dakota
Recorded hazard history: storm events since 1950, federal disaster declarations since 1953, flood insurance claims since 1978, and FEMA's risk index.
NCEI notes that Storm Data is compiled from a variety of sources including the National Weather Service, other federal, state and local agencies, the media and the public; that property and crop damage figures are estimates; and that some events are recorded by NWS forecast zone rather than by county. FEMA notes that NFIP claim records are redacted and aggregated to protect the privacy of policyholders. NCEI storm records through 30 Jun 2026; OpenFEMA declarations refreshed 1 Oct 2026; NFIP claims as of 8 Sep 2026.
Dewey County, South Dakota, has 814 weather events in the NCEI Storm Events record since 1950, most of them damaging wind.
That is 35.4 events per 100 square miles, below the South Dakota figure of 73.7, and 1,551.7 per 10,000 residents against 624.1 statewide.
37 events fall in the 12 months to 30 Jun 2026. NCEI attributes 3 deaths and 2 injuries to events in the county, with property damage estimated at $1.2M and crop damage at $3.0M.
FEMA has designated the county in 17 federal disaster declarations since 1953; the most recent is Covid-19 Pandemic (major disaster, 5 Apr 2020).
OpenFEMA lists no National Flood Insurance Program claims in the county.
FEMA's National Risk Index rates the county's overall risk as "Relatively Low" and its expected annual loss as "Relatively Low" ($22M a year across 18 hazards).
Compared with South Dakota and the United States
| Measure | Dewey County | South Dakota | US |
|---|---|---|---|
| Recorded events since 1950 | 814 | 55,877 | 1,977,440 |
| Events per 100 square miles | 35.4 | 73.7 | 56.0 |
| Events per 10,000 residents | 1,551.7 | 624.1 | 59.6 |
| Events in the last 12 months | 37 | 2,303 | 62,008 |
| Deaths recorded by NCEI | 3 | 147 | 26,435 |
| Property damage (NCEI estimates) | $1.2M | $1.1B | $575B |
| NFIP claims per 1,000 residents | 0.0 | 4.5 | 8.1 |
| Average paid NFIP claim | — | $21K | $43K |
| Claims per 100 policies in force, last 10 years | — | 30.7 | 16.1 |
County-recorded events plus zone-recorded events whose forecast zone is named for the county. State and US rows include events recorded only by forecast zone. Rates use 2021 Census population and land area.
Events by decade
Trend: 579 events in the 20 years to 2025 against 193 in the 20 years before. Reporting practice changed in 1996 and again with automated reports in the 2000s, so decade totals measure the record as much as the weather.
Events by type
Hazard pages exist for hail, tornado, flood, wind and winter where the county has at least 10 recorded events. "Other" covers heavy rain, debris flow, dust, funnel clouds and similar reports.
Largest recorded events
| Date | Event type | Group | Magnitude | Property damage | Crop damage | Deaths | Injuries | Geography |
|---|---|---|---|---|---|---|---|---|
| 1 Jan 2017 | Extreme Cold/Wind Chill | Cold | — | — | — | 2 | — | Forecast zone |
| 12 Jan 2024 | Extreme Cold/Wind Chill | Cold | — | — | — | 1 | — | Forecast zone |
| 8 Jun 1964 | Tornado | Tornado | F2 | — | — | — | 1 | County |
| 16 Dec 1996 | Blizzard | Winter | — | — | — | — | 1 | Forecast zone |
| 1 Jun 2019 | Flood | Flood | — | — | $2.9M | — | — | County |
| 5 Jun 2008 | Flood | Flood | — | $500K | $100K | — | — | County |
| 25 Dec 2016 | Ice Storm | Winter | — | $223K | — | — | — | Forecast zone |
| 1 Apr 2019 | Flood | Flood | — | $199K | — | — | — | County |
| 16 Jun 2010 | Flash Flood | Flood | — | $100K | — | — | — | County |
Ranked by deaths, then injuries, then NCEI's damage estimate. Deaths and injuries are NCEI counts (direct plus indirect); no personal details are recorded here.
Federal disaster declarations
| Declared | Number | Type | Incident | Title | Programs |
|---|---|---|---|---|---|
| 5 Apr 2020 | DR-4527 | Major disaster | Biological | Covid-19 Pandemic | Individual assistance |
| 5 Apr 2020 | DR-4527 | Major disaster | Biological | Covid-19 Pandemic | Individual assistance, Public assistance |
| 13 Mar 2020 | EM-3475 | Emergency | Biological | Covid-19 | Public assistance |
| 7 Jun 2019 | DR-4440 | Major disaster | Flood | Severe Winter Storm, Snowstorm, And Flooding | Individual assistance, Public assistance |
| 1 Feb 2017 | DR-4298 | Major disaster | Severe Storm | Severe Winter Storm | Public assistance |
| 28 Jul 2014 | DR-4186 | Major disaster | Flood | Severe Storms, Tornadoes, And Flooding | Public assistance |
| 8 Nov 2013 | DR-4155 | Major disaster | Severe Storm | Severe Winter Storm, Snowstorm, And Flooding | Individual assistance, Public assistance |
| 29 Jul 2010 | DR-1929 | Major disaster | Severe Storm | Severe Storms, Tornadoes, And Flooding | Public assistance |
| 10 Mar 2010 | DR-1887 | Major disaster | Severe Storm | Severe Winter Storm | Public assistance |
| 16 Jun 2009 | DR-1844 | Major disaster | Severe Storm | Severe Storms And Flooding | Public assistance |
| 12 Dec 2008 | DR-1811 | Major disaster | Snowstorm | Severe Winter Storm And Record And Near Record Snow | Public assistance |
| 9 Jul 2008 | DR-1774 | Major disaster | Severe Storm | Severe Storms And Flooding | Public assistance |
| 10 Sep 2005 | EM-3234 | Emergency | Coastal Storm | Hurricane Katrina Evacuation | Public assistance |
| 7 Apr 1997 | DR-1173 | Major disaster | Flood | Severe Flooding, Sever Winter Storms,Heavy Rains High Winds | Individual assistance, Public assistance |
| 10 Jan 1997 | DR-1156 | Major disaster | Severe Storm | Severe Winter Storms And Blizzard Conditions | Public assistance |
| 14 Mar 1995 | DR-1045 | Major disaster | Snowstorm | Severe Winter Storms | Public assistance |
| 17 Jun 1976 | EM-3015 | Emergency | Drought | Drought | Public assistance |
Declarations in which FEMA designated this county, from the OpenFEMA Disaster Declarations Summaries (v2). DR: major disaster; EM: emergency; FM: fire management assistance. Programs show whether individual or public assistance was made available.
Flood insurance claims
OpenFEMA lists no NFIP claims with this county's code.
National Risk Index
| Hazard (NRI) | Risk rating | Expected annual loss |
|---|---|---|
| Cold wave | $19,745,510 | |
| Inland flooding | $1,175,510 | |
| Wildfire | $317,633 | |
| Hail | $195,475 | |
| Tornado | $192,176 | |
| Winter weather | $159,170 | |
| Strong wind | $119,107 | |
| Ice storm | $94,378 | |
| Heat wave | $46,816 | |
| Lightning | $31,392 | |
| Drought | $10,648 | |
| Earthquake | $6,874 | |
| Landslide | $201 |
FEMA National Risk Index, December 2025 release. Ratings are FEMA's relative comparison of counties; expected annual loss is FEMA's modelled estimate of average yearly building, population and agriculture loss. See how to read the NRI.
Hurricane and tropical storm passes
No HURDAT2 track at tropical-storm strength passes within 100 miles of the county's centre point (through the 2025 season).
Questions and answers
How often does it hail in Dewey County, SD?
NCEI records 265 hail events in Dewey County since 1950, in 46 different years; that is about 3.4 recorded events a year. 82 reports were golf-ball size (1.75 in) or larger.
Has Dewey County had a tornado?
Yes. NCEI records 27 tornadoes in Dewey County since 1950, 4 of them rated (E)F2 or stronger. Tornado deaths recorded: 0.
When was the last federal disaster declaration for Dewey County?
5 Apr 2020: Covid-19 Pandemic, a major disaster declaration for biological. The county appears in 17 declarations since 1953.
How many flood insurance claims have been filed in Dewey County, and how much was paid?
OpenFEMA lists no NFIP claims in the county.
Is Dewey County in the National Risk Index's high-risk band?
FEMA's National Risk Index (December 2025) rates the county "Relatively Low" for overall risk, "Relatively Low" for expected annual loss, "Very High" for social vulnerability and "Very Low" for community resilience. These ratings are FEMA's relative comparison across all US counties.
How does Dewey County compare with the rest of South Dakota?
35.4 recorded events per 100 square miles against 73.7 statewide, and 0.0 NFIP claims per 1,000 residents against 4.5. The comparison table on this page shows each measure beside the state and national figures.
Provenance
Storm events: NOAA NCEI Storm Events Database, yearly details files through 30 Jun 2026 (public domain). Declarations: OpenFEMA DisasterDeclarationsSummaries v2, refreshed 1 Oct 2026. Flood claims: OpenFEMA NfipClaims v3 as of 8 Sep 2026; NfipMultipleLossProperties v1 (2 Aug 2026); NfipResidentialPenetrationRates v1 (3 Aug 2026). Risk index: FEMA National Risk Index, December 2025. Hurricane tracks: NHC HURDAT2 through 2025. Population and area: US Census Bureau, 2021 vintage. Built 1 Oct 2026; see the methodology and corrections pages. Hazard hubs: Hail · Tornado · Flood · Wind · Winter.