Union County
South Dakota — Natural Disaster Risk Assessment
Very LowComposite Risk Score
National percentile: 37th
Union County faces very low composite natural disaster risk (NRI Risk Index score 37.1, 37th national percentile), driven primarily by wildfire and winter weather exposure. Expected annual loss across all 18 hazard types is $16M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Top Hazards
All 18 Hazard Risks
| Wildfire | Low | 0.00 / yr | $447K |
| Winter Weather | Medium | 15.42 / yr | $256K |
| Drought | Medium | 27.26 / yr | $951K |
| Hail | Medium | 6.45 / yr | $917K |
| Tornado | Medium | 0.40 / yr | $3M |
| Ice Storm | Medium | 0.98 / yr | $272K |
| Riverine Flood | Low | 3.61 / yr | $9M |
| Landslide | Very Low | 0.08 / yr | $670 |
| Cold Wave | Low | 6.47 / yr | $734K |
| Heat Wave | Very Low | 6.47 / yr | $234K |
| Lightning | Low | 39.68 / yr | $164K |
| Strong Wind | Low | 4.09 / yr | $346K |
| Earthquake | Very Low | 0.00 / yr | $28K |
| 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 Union County?
Union County has a composite FEMA National Risk Index score of 37.1 out of 100, placing it in the Very Low category and the 37th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Union County?
The three highest-rated hazards are Wildfire (Low, $447K EAL), Winter Weather (Medium, $256K EAL), Drought (Medium, $951K EAL). These account for most of the county's expected annual losses.
How does Union County compare to other South Dakota counties?
Union County ranks #21 of 66 South Dakota counties for overall natural disaster risk, with a very 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. Union County's $16M EAL is a statistical average, not a guarantee for any specific year or address.