FEMA Records
16
Below median
South Dakota · FEMA + NOAA + National Risk Index
Dewey County, SD
16 FEMA disaster declarations (1976-2020), with a FEMA National Risk Index rating of Relatively Low. Most common hazard: Severe Storm.
- 16
- FEMA declarations
- 13
- Major disasters
- 79
- NRI risk · Relatively Low
- Severe Storm
- Top hazard
The verdict
Dewey County has a nationally busy FEMA history: 16 declarations, more than 27% of counties in this registry. But the state comparison tempers that reading: the total is 16% below the South Dakota county mean. FEMA's separate National Risk Index places the county in the riskiest 21%; that score models loss and vulnerability rather than counting declarations.
- Riskiest 21%
- of U.S. counties for FEMA National Risk Index score
- Relatively Low
- FEMA National Risk Index rating
- 16
- FEMA declarations vs 21 national county avg
- 7
- severe storm declarations, the most common hazard here
FEMA's National Risk Index and its declaration registry are separate measures. This county's registry includes Major Disaster (DR) and Emergency (EM) records; an EM authorizes a narrower set of federal assistance than a DR.
How does Dewey County compare?
Dewey County vs. all counties in this dataset
FEMA disaster declarations, all-time
16 27th percentile higher than 27% of 3,266 counties
Each bar is a band; taller bars hold more counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source FEMA Disaster Declarations Summaries v2 · 2026-08-03
Dewey County's FEMA Risk Index score
FEMA National Risk Index composite score vs. the South Dakota county average
What does Dewey County's hazard record show?
FEMA National Risk Index
This county sits among the highest-risk counties nationally on FEMA's National Risk Index, a composite score of 78.7/100 (Relatively Low). Expected Annual Loss is rated Relatively Low (roughly $22.1M in annualized losses). Social vulnerability reads Very High and community resilience Very Low, both critical modifiers of realized harm here. Of the 18 hazards FEMA models, Cold Wave stands out as the sharpest exposure here, rated Very High. FEMA's modeled frequency puts that hazard at an average of 9.2 times per year here, based on 175 historical events on record.
Declaration frequency
Nationally, Dewey County's 16 FEMA records form a high-volume history; within South Dakota, however, the count is 16% below the county mean. 13 entries carry the Major Disaster classification. The largest incident group is Severe Storm, appearing 7 times. The full 44-year record averages 0.4 declarations annually. A DR label alone does not say whether Individual Assistance, Public Assistance, or both followed.
Reading the federal records together
No paid-claim row for this county appears in the NFIP county table used by PlainHazard. That absence is not evidence that flooding never occurred: the register observes claims under federal flood-insurance policies, not uninsured losses, emergency reports, or every flood outside the program. The FEMA declaration history below is therefore the available federal-action record on this page.
Start with the state benchmark: a South Dakota county averages 19.0 federal declaration records, while Dewey County has 16. The gap is 16% below that mean. Fewer entries indicate a quieter history of recorded federal actions, not immunity from a hazard and not a prediction about what happens next.
58 /100
Historical Activity Index
High historical activity
Dewey County, SD · PlainHazard-derived composite from federal records
This 0–100 index is an explicit PlainHazard composite from FEMA declaration history only on the county surface (this DB has no county-level NOAA damage row) . It is not FEMA's National Risk Index, not a forecast, and not a safety, insurance, or preparedness rating. Open the calculator · Methodology
FEMA Declarations (1953–present) Moderate
12/30
16 OpenFEMA declarations, full ingest window (0.8x national county average)
County Disaster Density Moderate
11/25
16 declarations (0.8x state county average of 19)
Major Disaster Share Very High
20/25
13 of 16 declarations are major disasters (81%)
Hazard Diversity Very High
15/20
6 different disaster types declared in Dewey County
Historical Declaration Activity
Activity Band
High
vs. South Dakota Avg
-16%
State avg: 19.0
vs. National Avg
-23%
National avg: 20.7
Avg Per Year
0.4
Over 44 years
FEMA NRI 8-hazard radar - Dewey County
How to read this radar
Each axis: NRI risk rating (Very Low-Very High) on a 0-100 scale. Rounder = broad exposure; spiky = one or two hazards dominate.
Major Disaster share
81%
Mostly major
NRI risk score
79
Relatively Low
Source: FEMA National Risk Index Per-county per-hazard ratings, December 2025 release
How often does each hazard strike Dewey County?
FEMA's National Risk Index models a historical event count and an annualized frequency for each hazard type. Most hazards are expressed as modeled occurrences per year; FEMA expresses drought and heat-wave frequency as event-days per year. These modeled frequencies are not forecasts.
| Hazard | NRI Risk Rating | Recurrence |
|---|---|---|
| Cold Wave | Very High | an average of 9.2 times per year |
| Winter Weather | Relatively High | an average of 17 times per year |
| Wildfire | Relatively Low | roughly once every 851 years |
| Ice Storm | Relatively Moderate | roughly once every 2 years |
| Hail | Relatively Low | an average of 2.8 times per year |
| Landslide | Very Low | an average of 1 time per year |
| Drought | Very Low | 50 modeled event-days per year |
| Tornado | Very Low | roughly once every 2 years |
| Heat Wave | Very Low | 2.8 modeled event-days per year |
| Strong Wind | Relatively Low | an average of 2.3 times per year |
| Riverine Flooding | Very Low | roughly once every 1 years |
| Lightning | Very Low | an average of 33 times per year |
| Earthquake | Very Low | roughly once every 4,762 years |
Source: FEMA National Risk Index Modeled annualized frequency; drought and heat wave use event-days/year, December 2025 release
Disaster Types
Severe Storm 7
Flood 3
Biological 2
Snowstorm 2
Coastal Storm 1
Drought 1
What Severe Storm declarations mean here
Severe Storm is the most frequent declaration type on Dewey County's record, 44% of its declarations. In FEMA's vocabulary this covers convective weather: thunderstorm straight-line winds, large hail, and the multi-day outbreaks that often carry embedded tornadoes. Activity is heaviest in spring and summer, though the season varies by region.
These events behave differently from a hurricane on paper. Damage tends to be distributed along a storm track rather than concentrated on a coastline, and a declaration typically follows an outbreak that crossed several counties over a few days, not a single point of impact. Because the qualifying threshold is the cost of uninsured public and individual losses rather than storm intensity, two similar storms can produce a declaration in one year and none in another.
Declaration counts describe past federal action. They are a record of what was declared, not a forecast of future hazard probability.
Declaration Types
What DR / EM / FM mean
FEMA categorizes declarations as Major Disasters (DR), Emergencies (EM), or Fire Management Assistance (FM).
Major Disaster - 13 81.3%
of all 16 declarations
Emergency - 3 18.8%
of all 16 declarations
FEMA Declarations Timeline
| Year | Declarations | |
|---|---|---|
| 2020 | 2 | |
| 2019 | 1 | |
| 2017 | 1 | |
| 2014 | 2 | |
| 2010 | 2 | |
| 2009 | 2 | |
| 2008 | 1 | |
| 2005 | 1 | |
| 1997 | 2 | |
| 1995 | 1 | |
| 1976 | 1 | |
Disaster Declarations
How the 16 FEMA declarations break into federal action codes (DR / EM / FM). Same DISTINCT grain as the table below.
Download these 16 declarations as CSV . FEMA source data is public domain; our derived presentation is CC0.
| DR# | Title | Type | Incident | Date |
|---|---|---|---|---|
| 4527 | COVID-19 PANDEMIC | DR | Biological | 2020-04-05 |
| 3475 | COVID-19 | EM | Biological | 2020-03-13 |
| 4440 | SEVERE WINTER STORM, SNOWSTORM, AND FLOODING | DR | Flood | 2019-06-07 |
| 4298 | SEVERE WINTER STORM | DR | Severe Storm | 2017-02-01 |
| 4186 | SEVERE STORMS, TORNADOES, AND FLOODING | DR | Flood | 2014-07-28 |
| 4155 | SEVERE WINTER STORM, SNOWSTORM, AND FLOODING | DR | Severe Storm | 2013-11-08 |
| 1929 | SEVERE STORMS, TORNADOES, AND FLOODING | DR | Severe Storm | 2010-07-29 |
| 1887 | SEVERE WINTER STORM | DR | Severe Storm | 2010-03-10 |
| 1844 | SEVERE STORMS AND FLOODING | DR | Severe Storm | 2009-06-16 |
| 1811 | SEVERE WINTER STORM AND RECORD AND NEAR RECORD SNOW | DR | Snowstorm | 2008-12-12 |
| 1774 | SEVERE STORMS AND FLOODING | DR | Severe Storm | 2008-07-09 |
| 3234 | HURRICANE KATRINA EVACUATION | EM | Coastal Storm | 2005-09-10 |
| 1173 | SEVERE FLOODING, SEVER WINTER STORMS,HEAVY RAINS HIGH WINDS | DR | Flood | 1997-04-07 |
| 1156 | SEVERE WINTER STORMS AND BLIZZARD CONDITIONS | DR | Severe Storm | 1997-01-10 |
| 1045 | SEVERE WINTER STORMS | DR | Snowstorm | 1995-03-14 |
| 3015 | DROUGHT | EM | Drought | 1976-06-17 |
Storm Events in South Dakota
Statewide NOAA context only. PlainHazard does not currently attribute these state totals to Dewey County.
| Storm Type | Events | Fatalities | Injuries | Property Damage |
|---|---|---|---|---|
| Thunderstorm Wind | 5,388 | 7 | 21 | $10.7M |
| Hail | 4,801 | 0 | 3 | $4.5M |
| High Wind | 2,277 | 0 | 1 | $35.0K |
| Winter Weather | 2,125 | 20 | 50 | $133.0K |
| Flood | 1,523 | 5 | 0 | $196.2M |
Source: NOAA Storm Events Database State-level aggregated data, 2015-2025
FEMA National Risk Index
Overall Risk
Relatively Low
Score: 78.7/100
Expected Annual Loss
Relatively Low
$22.1M/year
Social Vulnerability
Very High
Community Resilience
Very Low
Hazard Risk Breakdown
Cold Wave Very High
Winter Weather Relatively High
Wildfire Relatively Low
Ice Storm Relatively Moderate
Hail Relatively Low
Landslide Very Low
Drought Very Low
Tornado Very Low
Heat Wave Very Low
Strong Wind Relatively Low
Riverine Flooding Very Low
Lightning Very Low
Earthquake Very Low
Source: FEMA National Risk Index (NRI) Ratings reflect relative scores among all US counties. Data: hazards.fema.gov/nri
The model's sharpest exposure here: Cold Wave
Cold Wave measures exposure to extreme cold rather than to snow. Its harm is concentrated in health effects, burst infrastructure and energy demand spikes, and it falls hardest where the building stock and the grid were not built with sustained cold in mind.
Worth noting for Dewey County: the model and the federal record do NOT point at the same hazard. Cold Wave carries the highest modeled rating (Very High), while the county's declaration history is led by Severe Storm. That is not a contradiction, the two measure genuinely different things. Declarations record federal ACTION, which requires damage costly enough to exceed state and local capacity; the Risk Index models EXPECTED annual loss across all 18 hazards whether or not any declaration ever followed. A hazard can be the county's largest modeled exposure and never once have driven a declaration.
National Risk Index ratings are modeled estimates of expected annual loss, not predictions of what will happen in any given year.
Data-matched county comparisons
Dewey County's closest FEMA peer: Delaware County, OH
Comparisons use published FEMA declaration fields plus the National Risk Index composite for Dewey County. Record similarity, not a safety rating.
Similar modeled NRI score
Dewey County: NRI composite 78.7 (Relatively Low).
Similar Major-disaster share
Dewey County: 13 of 16 of its declarations are Major.
Closest declaration profiles
Dewey County shows 16 FEMA declarations, led by Severe Storm.
How these peers are chosen
Cohort: Published U.S. county equivalents outside the source state or territory. Each metric keeps six ETL candidates; three unique destinations are shown after de-duplicating across axes. Declaration-volume ranking combines count and Major-disaster share and prefers a different leading incident type; Major-share ranks the Major fraction adjusted for volume; NRI ranks the modeled composite score only.
Retained FEMA snapshot feed for Dewey County - capture-dated entries only.
Further reading for this county
Most disaster-prone counties
With 16 FEMA declarations, Dewey County sits in the high-volume declaration band - see how that count ranks against other U.S. counties.
More PlainHazard guides
- Most disaster-prone counties - U.S. counties ranked by FEMA declaration totals.
- Understanding disaster data - declarations vs storm events vs NRI scores.
- Preparing for natural disasters - household checklist (not county-specific advice).
Related
Frequently Asked Questions
What is the most common disaster type in Dewey County?
The most common disaster type in Dewey County is Severe Storm, with 7 declarations. Other disaster types include Flood (3), Biological (2), Snowstorm (2).
How does Dewey County's FEMA declaration record compare with the South Dakota average?
The typical South Dakota county has 19.0 FEMA declaration records; Dewey County has 16, or 16% fewer. Against the national county mean of 20.7, this county's total is 23% lower. The comparison is historical and says nothing about the probability of a future event.
How many major FEMA disaster declarations has Dewey County received?
Dewey County has received 13 major disaster declarations, representing 81% of all 16 disaster declarations.
What was the worst year for disasters in Dewey County?
The most active year for disaster declarations in Dewey County was 1997, with 2 declarations. The county has FEMA disaster data spanning 1976 to 2020.
What is the FEMA National Risk Index score for Dewey County?
According to the FEMA National Risk Index, Dewey County, South Dakota has an overall risk score of 78.7 out of 100 (Relatively Low). The county's social vulnerability rating is Very High and community resilience is Very Low. The Expected Annual Loss (EAL) score is Relatively Low, representing $22.1M in annualized losses.
Which natural hazard poses the greatest risk to Dewey County?
FEMA's NRI data points to Dewey County is Cold Wave (risk rating: Very High). Other significant hazards include Winter Weather (Relatively High) and Wildfire (Relatively Low). FEMA's modeled event frequency puts cold wave here at an average of 9.2 times per year, drawn from 175 historical events on record. FEMA derives these ratings from historical event frequency, the assets exposed, and the community's vulnerability profile.
Data Sources & Methodology
Disaster declaration data comes from the FEMA OpenFEMA Disaster Declarations Summaries v2 API, which includes all federally declared disasters, emergencies, and fire management assistance grants.
Storm event data is sourced from the NOAA Storm Events Database (2015-2025), which tracks significant weather events including thunderstorms, tornadoes, floods, and winter storms.
This data is provided for informational purposes only. FEMA disaster declarations represent federal response actions and may not capture all local emergencies or weather events.
What this means for Dewey County
Against a South Dakota county mean of 19 declarations, Dewey County, SD records 16, or 16% fewer. PlainHazard classifies that historical total as high activity.
- Major Disaster is the largest group (13 of 16) in a declaration history that remains below its state benchmark; frequency here is not a forecast. South Dakota overview
- Nationally the county exceeds 27% of recorded county totals, but its own South Dakota benchmark is higher. The ranking keeps those two contexts separate. Most-disaster rankings
- With no NFIP county row, the declaration register and modeled NRI remain distinct evidence rather than substitutes for a claims history. Disaster-data guide
A below-average federal record is not a safety guarantee. Use National Weather Service alerts and local emergency-management notices for present conditions, not this historical comparison.
PlainHazard derives this profile from FEMA's Disaster Declarations Summaries and National Risk Index data. The declaration comparison covers 3,266 U.S. counties and county equivalents in this database, refreshed as of 2026-08-03. Read our methodology - how this data is sourced, computed, and verified.
All federal data sources used on this page
- FEMA OpenFEMA, Disaster Declarations Summaries v2 - all federally-declared disasters for this county. fema.gov/openfema/disaster-declarations
- FEMA National Risk Index (NRI) - per-county per-hazard risk ratings and expected annual loss. hazards.fema.gov/nri
- NOAA NCEI Storm Events Database - state-level storm/severe-weather event records, 2015-2025. ncdc.noaa.gov/stormevents
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainHazard Editorial
Verify with FEMA → · Verify with FEMA NRI → · Verify with NOAA →
Every figure on PlainHazard is rendered directly from FEMA federal disaster data, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or national statistics report, the data & editorial changelog, or report a data error.