Big Horn County, Wyoming: Natural Disaster Risk and History
Big Horn County, Wyoming has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 31.1 out of 100, higher than about 31% of US counties, with landslides, earthquakes and wildfires scoring highest of its 18 hazards and $8.9 million a year in expected losses.
OpenFEMA lists 2 federal disaster declarations that included Big Horn County since 1978, not counting 2 for COVID-19; the latest is DR-4007-WY (Severe Storms, Flooding, and Landslides, declared 22 July 2011). NOAA's Storm Prediction Center recorded 32 tornadoes touching Big Horn County from 1950 to 2025.
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Population 11,503 Buildings worth $3.5 billion Area 3,190 sq mi Risk rank in Wyoming 12 of 23 FIPS 56003
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Landslide | Relatively High | 97.9 | $493,309 | about 2.1 a year | — |
| Earthquake | Relatively Low | 61.4 | $424,845 | about once every 355 years | — |
| Wildfire | Very Low | 61.4 | $80,910 | rarer than once in 1,000 years | — |
| Cold wave | Relatively Low | 57.9 | $1.1 million | about 1.3 a year | 25 |
| Inland flooding | Relatively Low | 52.4 | $6.2 million | about once every 1.1 years | 25 |
| Winter weather | Relatively Low | 45.9 | $48,923 | about 11 a year | 205 |
| Drought | Relatively Low | 39.3 | $53,957 | about 86 a year | 2,499 |
| Lightning | Relatively Low | 37.0 | $125,761 | about 34 a year | 77,549 strikes |
| Volcanic activity | Very Low | 33.2 | $3 | rarer than once in 1,000 years | 1 |
| Avalanche | Very Low | 32.3 | $110 | about once every 100 years | 0 |
| Hail | Very Low | 26.6 | $87,805 | about once every 1.4 years | 26 |
| Tornado | Very Low | 16.7 | $155,238 | about once every 4.3 years | 23 |
| Strong wind | Very Low | 12.0 | $79,985 | about once every 2.4 years | 17 |
| Ice storm | Very Low | 8.9 | $3,946 | about once every 67 years | 0 |
| Heat wave | Very Low | 8.8 | $12,499 | about once every 4.5 years | 0 |
| Coastal flooding | Not Applicable | — | — | — | — |
| Hurricane | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 2
Most common: Severe Storm 1, Flood 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 1 | Flood |
| 2010s | 1 | Severe Storm |
The last 2
Widest declarations that included Big Horn County
- Severe Storms, Flooding, and Landslides (2011, DR-4007-WY): 15 Wyoming counties designated.
- Severe Storms, Flooding & Mudslides (1978, DR-557-WY): 12 Wyoming counties designated.
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Wyoming also had 1 statewide declaration with no county list.
Tornado record since 1950 32
| Tornadoes touching the county | 32 |
|---|---|
| Strongest-rated | (E)F3 ×1 |
| Peak month | June (20) |
| Deadliest | 26 Jun 1959, F2, 9.2 mi path, 1 killed, 1 injured |
| Longest path | 1 Jun 2005, F0, 10 mi path |
| Most recent | 12 Jun 2017, EF0, 3.1 mi path |
| Deaths / injuries on those paths | 1 / 2 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 15 | 10 | 6 | 1 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 4 | 6 | 4 | 7 | 6 | 3 | 0 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Big Horn County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Big Horn County (this page) | — | Very Low | 31.1 | Landslide |
| Washakie County | 74 km | Very Low | 24.4 | Landslide |
| Sheridan County | 93 km | Relatively Low | 65.2 | Wildfire |
| Hot Springs County | 97 km | Very Low | 16.1 | Landslide |
| Big Horn County, MT | 107 km | Relatively Low | 57.2 | Strong wind |
| Carbon County, MT | 113 km | Relatively Low | 59.8 | Landslide |
Nearest by distance between county centres. Every county in Wyoming, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Moderate 52.6 |
|---|---|
| Community resilience | Very Low 7.7 |
| Community risk factor | 1.19 |
| Expected annual loss, all hazards | $8.9 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Big Horn County's main hazards
- Right now: National Weather Service alerts for Wyoming · all official warnings on Global Incident Tracker.
- Landslide: Landslides recorded
- Earthquake: Earthquakes today · Earthquake safety guide
- Wildfire: US wildfires now · Wildfire smoke: what protects you
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Big Horn County
What natural disasters is Big Horn County, Wyoming most at risk from?
Big Horn County, Wyoming has a Very Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 31.1 out of 100, higher than about 31% of US counties, with landslides, earthquakes and wildfires scoring highest of its 18 hazards and $8.9 million a year in expected losses.
How many federal disaster declarations has Big Horn County had?
OpenFEMA lists 2 federal disaster declarations that included Big Horn County since 1978, not counting 2 for COVID-19; the latest is DR-4007-WY (Severe Storms, Flooding, and Landslides, declared 22 July 2011). Another 1 Wyoming declarations were made statewide without a county list.
How many tornadoes have hit Big Horn County?
NOAA's Storm Prediction Center recorded 32 tornadoes touching Big Horn County from 1950 to 2025. The deadliest: 26 Jun 1959, F2, 9.2 mi path, 1 killed, 1 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.