Walworth County, South Dakota Natural Disaster Risk
FEMA National Risk Index assessment · SD
Very LowComposite Risk Score
National percentile: 40th
Walworth County faces very low composite natural disaster risk (NRI Risk Index score 39.5, 40th national percentile), driven primarily by cold wave and winter weather exposure. Expected annual loss across all 18 hazard types is $10M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Walworth County at very low composite risk, with a National Risk Index score of 39.5 out of 100 — placing it in the 40th 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.
Risk here concentrates in cold wave (prolonged spells of dangerously low temperatures) at Medium risk — $5M in expected annual loss and about 11.16 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $196K in expected annual loss and about 17.95 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $361K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $10M in expected annual loss for a population of 5K.
Beyond physical exposure, Walworth County has a high social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). Higher vulnerability is partly offset by strong community resilience and recovery capacity.
The county's disaster history tells the same story: Walworth County has received 12 federal disaster declarations since 1976, including 5 for flood events and 2 for biological events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 66 South Dakota counties, Walworth County ranks #17 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Cold Wave | Medium | 11.16 / yr | $5M |
| Winter Weather | Medium | 17.95 / yr | $196K |
| Wildfire | Low | 0.00 / yr | $361K |
| Hail | Low | 3.23 / yr | $356K |
| Drought | Low | 20.95 / yr | $66K |
| Riverine Flood | Very Low | 0.61 / yr | $3M |
| Tornado | Low | 0.23 / yr | $367K |
| Ice Storm | Very Low | 0.57 / yr | $22K |
| Strong Wind | Low | 2.18 / yr | $134K |
| Heat Wave | Very Low | 2.74 / yr | $44K |
| Lightning | Very Low | 31.71 / yr | $31K |
| Earthquake | Very Low | 0.00 / yr | $6K |
| Landslide | Very Low | 0.11 / yr | $5 |
| 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
Walworth County has received 12 federal disaster declarations since 1976, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Flood (5), Biological (2), Severe Storm (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2019 | Flood | Severe Storms and Flooding |
| June 2019 | Flood | Severe Winter Storm, Snowstorm, and Flooding |
| March 2010 | Severe Storm | Severe Winter Storm |
| September 2005 | Coastal Storm | Hurricane Katrina Evacuation |
| April 1997 | Flood | Severe Flooding, Sever Winter Storms,Heavy Rains High Winds |
| January 1997 | Severe Storm | Severe Winter Storms and Blizzard Conditions |
| May 1995 | Flood | Flooding |
| March 1995 | Snowstorm | Severe Winter Storms |
Showing the 10 most recent of 12 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Walworth County?
Walworth County has a composite FEMA National Risk Index score of 39.5 out of 100, placing it in the Very Low category and the 40th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Walworth County?
The three highest-rated hazards are Cold Wave (Medium, $5M EAL), Winter Weather (Medium, $196K EAL), Wildfire (Low, $361K EAL). These account for most of the county's expected annual losses.
How does Walworth County compare to other South Dakota counties?
Walworth County ranks #17 of 66 South Dakota counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Walworth County had?
FEMA records 12 federal disaster declarations for Walworth County since 1976, most often 5 for flood events and 2 for biological events. The most recent was Covid-19 Pandemic, declared in April 2020.
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. Walworth County's $10M EAL is a statistical average, not a guarantee for any specific year or address.