Big Horn County, Wyoming Natural Disaster Risk
FEMA National Risk Index assessment · WY
Very LowComposite Risk Score
National percentile: 31th
Big Horn County faces very low composite natural disaster risk (NRI Risk Index score 31.1, 31th national percentile), driven primarily by landslide and earthquake exposure. Expected annual loss across all 18 hazard types is $9M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Big Horn County is very low, with a National Risk Index score of 31.1 out of 100 — placing it in the 31st 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 landslide (downhill movement of rock, soil, and debris on unstable slopes) at High risk — $493K in expected annual loss and about 2.07 events per year; earthquake (ground shaking from sudden movement along geologic faults) at Low risk — $425K in expected annual loss and about 0.00 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at Very Low risk — $81K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $9M in expected annual loss for a population of 12K.
Beyond physical exposure, Big Horn County has a medium 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). Both measures sit toward the lower end, indicating relatively modest population sensitivity.
The federal record bears this out: Big Horn County has received 4 federal disaster declarations since 1978, including 2 for biological events and 1 for severe storm events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 23 Wyoming counties, Big Horn County ranks #12 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | High | 2.07 / yr | $493K |
| Earthquake | Low | 0.00 / yr | $425K |
| Wildfire | Very Low | 0.00 / yr | $81K |
| Cold Wave | Low | 1.31 / yr | $1M |
| Riverine Flood | Low | 0.89 / yr | $6M |
| Winter Weather | Low | 10.82 / yr | $49K |
| Drought | Low | 85.63 / yr | $54K |
| Lightning | Low | 33.67 / yr | $126K |
| Volcanic Activity | Very Low | 0.00 / yr | $3 |
| Avalanche | Very Low | 0.01 / yr | $110 |
| Hail | Very Low | 0.69 / yr | $88K |
| Tornado | Very Low | 0.24 / yr | $155K |
| Strong Wind | Very Low | 0.42 / yr | $80K |
| Ice Storm | Very Low | 0.01 / yr | $4K |
| Heat Wave | Very Low | 0.22 / yr | $12K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Big Horn County has received 4 federal disaster declarations since 1978, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Severe Storm (1), Flood (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| July 2011 | Severe Storm | Severe Storms, Flooding, and Landslides |
| May 1978 | Flood | Severe Storms, Flooding & Mudslides |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Big Horn County?
Big Horn County has a composite FEMA National Risk Index score of 31.1 out of 100, placing it in the Very Low category and the 31th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Big Horn County?
The three highest-rated hazards are Landslide (High, $493K EAL), Earthquake (Low, $425K EAL), Wildfire (Very Low, $81K EAL). These account for most of the county's expected annual losses.
How does Big Horn County compare to other Wyoming counties?
Big Horn County ranks #12 of 23 Wyoming counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Big Horn County had?
FEMA records 4 federal disaster declarations for Big Horn County since 1978, most often 2 for biological events and 1 for severe storm 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. Big Horn County's $9M EAL is a statistical average, not a guarantee for any specific year or address.