Mellette County, South Dakota Natural Disaster Risk
FEMA National Risk Index assessment · SD
Very LowComposite Risk Score
National percentile: 5th
Mellette County faces very low composite natural disaster risk (NRI Risk Index score 5.2, 5th national percentile), driven primarily by wildfire and winter weather exposure. Expected annual loss across all 18 hazard types is $2M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Mellette County carries a very low composite natural disaster risk, with a National Risk Index score of 5.2 out of 100 — placing it in the 5th 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.
Most of Mellette County's expected losses come from wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $348K in expected annual loss and about 0.00 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at Low risk — $54K in expected annual loss and about 14.58 events per year; and cold wave (prolonged spells of dangerously low temperatures) at Low risk — $443K in expected annual loss and about 5.47 events per year. Across all hazards, FEMA estimates $2M in expected annual loss for a population of 2K.
Beyond physical exposure, Mellette County has a very high social vulnerability rating (how susceptible the population is to harm) and a very low community resilience rating (its capacity to prepare for and recover from disasters). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
The county's disaster history tells the same story: Mellette County has received 14 federal disaster declarations since 1976, including 4 for flood events and 4 for severe storm events. The most recent was Severe Winter Storms and Snowstorm (winter storm), declared in February 2023.
Among 66 South Dakota counties, Mellette County ranks #58 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Wildfire | Low | 0.00 / yr | $348K |
| Winter Weather | Low | 14.58 / yr | $54K |
| Cold Wave | Low | 5.47 / yr | $443K |
| Ice Storm | Low | 0.31 / yr | $23K |
| Drought | Very Low | 42.95 / yr | $16K |
| Landslide | Very Low | 0.63 / yr | $97 |
| Hail | Very Low | 3.32 / yr | $48K |
| Tornado | Very Low | 0.35 / yr | $133K |
| Strong Wind | Low | 2.66 / yr | $88K |
| Earthquake | Very Low | 0.00 / yr | $11K |
| Heat Wave | Very Low | 3.74 / yr | $21K |
| Lightning | Very Low | 37.19 / yr | $22K |
| Riverine Flood | Very Low | 0.54 / yr | $657K |
| 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
Mellette County has received 14 federal disaster declarations since 1976, most recently Severe Winter Storms and Snowstorm in February 2023. Most frequent causes: Flood (4), Severe Storm (4), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| February 2023 | Winter Storm | Severe Winter Storms and Snowstorm |
| 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 and Snowstorm |
| December 2008 | Snowstorm | Severe Winter Storm and Record and Near Record Snow |
| July 2008 | Severe Storm | Severe Storms and Flooding |
| September 2005 | Coastal Storm | Hurricane Katrina Evacuation |
| July 2004 | Severe Storm | Severe Storms and Flooding |
Showing the 10 most recent of 14 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Mellette County?
Mellette County has a composite FEMA National Risk Index score of 5.2 out of 100, placing it in the Very Low category and the 5th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Mellette County?
The three highest-rated hazards are Wildfire (Low, $348K EAL), Winter Weather (Low, $54K EAL), Cold Wave (Low, $443K EAL). These account for most of the county's expected annual losses.
How does Mellette County compare to other South Dakota counties?
Mellette County ranks #58 of 66 South Dakota counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Mellette County had?
FEMA records 14 federal disaster declarations for Mellette County since 1976, most often 4 for flood events and 4 for severe storm events. The most recent was Severe Winter Storms and Snowstorm, declared in February 2023.
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. Mellette County's $2M EAL is a statistical average, not a guarantee for any specific year or address.