Day County, South Dakota Natural Disaster Risk
FEMA National Risk Index assessment · SD
Very LowComposite Risk Score
National percentile: 28th
Day County faces very low composite natural disaster risk (NRI Risk Index score 27.6, 28th national percentile), driven primarily by winter weather and strong wind exposure. Expected annual loss across all 18 hazard types is $7M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Day County is very low, with a National Risk Index score of 27.6 out of 100 — placing it in the 28th 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.
The county's risk is driven primarily by winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $217K in expected annual loss and about 22.58 events per year; strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Medium risk — $1M in expected annual loss and about 2.91 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $259K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $7M in expected annual loss for a population of 5K.
Beyond physical exposure, Day 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 federal record bears this out: Day County has received 24 federal disaster declarations since 1976, including 10 for severe storm events and 9 for flood events. The most recent was Flooding (flood), declared in July 2023.
Among 66 South Dakota counties, Day County ranks #26 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | Medium | 22.58 / yr | $217K |
| Strong Wind | Medium | 2.91 / yr | $1M |
| Wildfire | Low | 0.00 / yr | $259K |
| Ice Storm | Medium | 0.51 / yr | $243K |
| Cold Wave | Medium | 14.11 / yr | $2M |
| Hail | Low | 3.98 / yr | $416K |
| Landslide | Very Low | 0.15 / yr | $599 |
| Tornado | Low | 0.59 / yr | $695K |
| Heat Wave | Very Low | 2.47 / yr | $65K |
| Riverine Flood | Very Low | 1.11 / yr | $2M |
| Earthquake | Very Low | 0.00 / yr | $12K |
| Drought | Very Low | 0.10 / yr | $126 |
| Lightning | Very Low | 32.54 / yr | $8K |
| 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
Day County has received 24 federal disaster declarations since 1976, most recently Flooding in July 2023. Most frequent causes: Severe Storm (10), Flood (9), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| July 2023 | Flood | Flooding |
| February 2023 | Winter Storm | Severe Winter Storms and Snowstorm |
| June 2022 | Severe Storm | Severe Storm, Straight-Line Winds, Tornadoes, and Flooding |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| November 2019 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| June 2019 | Flood | Severe Winter Storm, Snowstorm, and Flooding |
| February 2017 | Severe Storm | Severe Winter Storm |
| May 2011 | Flood | Flooding |
| May 2010 | Flood | Flooding |
Showing the 10 most recent of 24 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Day County?
Day County has a composite FEMA National Risk Index score of 27.6 out of 100, placing it in the Very Low category and the 28th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Day County?
The three highest-rated hazards are Winter Weather (Medium, $217K EAL), Strong Wind (Medium, $1M EAL), Wildfire (Low, $259K EAL). These account for most of the county's expected annual losses.
How does Day County compare to other South Dakota counties?
Day County ranks #26 of 66 South Dakota counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Day County had?
FEMA records 24 federal disaster declarations for Day County since 1976, most often 10 for severe storm events and 9 for flood events. The most recent was Flooding, declared in July 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. Day County's $7M EAL is a statistical average, not a guarantee for any specific year or address.