Dewey County
South Dakota — Natural Disaster Risk Assessment
LowComposite Risk Score
National percentile: 79th
Dewey County faces low composite natural disaster risk (NRI Risk Index score 78.7, 79th national percentile), driven primarily by cold wave and winter weather exposure. Expected annual loss across all 18 hazard types is $22M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Top Hazards
All 18 Hazard Risks
| Cold Wave | Very High | 9.21 / yr | $20M |
| Winter Weather | High | 16.58 / yr | $159K |
| Wildfire | Low | 0.00 / yr | $318K |
| Ice Storm | Medium | 0.55 / yr | $94K |
| Hail | Low | 2.85 / yr | $195K |
| Landslide | Very Low | 1.04 / yr | $201 |
| Drought | Very Low | 50.02 / yr | $11K |
| Tornado | Very Low | 0.54 / yr | $192K |
| Heat Wave | Very Low | 2.84 / yr | $47K |
| Strong Wind | Low | 2.32 / yr | $119K |
| Riverine Flood | Very Low | 0.96 / yr | $1M |
| Lightning | Very Low | 32.69 / yr | $31K |
| Earthquake | Very Low | 0.00 / yr | $7K |
| 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 |
Frequently Asked Questions
What is the overall natural disaster risk for Dewey County?
Dewey County has a composite FEMA National Risk Index score of 78.7 out of 100, placing it in the Low category and the 79th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Dewey County?
The three highest-rated hazards are Cold Wave (Very High, $20M EAL), Winter Weather (High, $159K EAL), Wildfire (Low, $318K EAL). These account for most of the county's expected annual losses.
How does Dewey County compare to other South Dakota counties?
Dewey County ranks #2 of 66 South Dakota counties for overall natural disaster risk, with a low rating.
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. Dewey County's $22M EAL is a statistical average, not a guarantee for any specific year or address.