Twin Falls County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
LowComposite Risk Score
National percentile: 47th
Twin Falls County faces low composite natural disaster risk (NRI Risk Index score 46.9, 47th national percentile), driven primarily by winter weather and wildfire exposure. Expected annual loss across all 18 hazard types is $17M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Twin Falls County carries a low composite natural disaster risk, with a National Risk Index score of 46.9 out of 100 — placing it in the 47th national percentile and below the national average for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Twin Falls County's expected losses come from winter weather (heavy snow, blizzards, and hazardous winter conditions) at High risk — $779K in expected annual loss and about 11.81 events per year; wildfire (uncontrolled fires that spread across wildland and into communities) at Medium risk — $3M in expected annual loss and about 0.02 events per year; and landslide (downhill movement of rock, soil, and debris on unstable slopes) at Medium risk — $95K in expected annual loss and about 0.29 events per year. Across all hazards, FEMA estimates $17M in expected annual loss for a population of 90K.
Beyond physical exposure, Twin Falls County has a low social vulnerability rating (how susceptible the population is to harm) and a medium 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: Twin Falls County has received 4 federal disaster declarations since 2005, including 2 for biological events and 1 for flood events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Twin Falls County ranks #17 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | High | 11.81 / yr | $779K |
| Wildfire | Medium | 0.02 / yr | $3M |
| Landslide | Medium | 0.29 / yr | $95K |
| Heat Wave | Medium | 3.23 / yr | $2M |
| Earthquake | Low | 0.00 / yr | $1M |
| Ice Storm | Low | 0.05 / yr | $128K |
| Volcanic Activity | Very Low | 0.00 / yr | $22 |
| Lightning | Low | 23.79 / yr | $304K |
| Avalanche | Very Low | 0.01 / yr | $865 |
| Riverine Flood | Low | 0.32 / yr | $8M |
| Cold Wave | Low | 0.24 / yr | $770K |
| Strong Wind | Low | 0.31 / yr | $414K |
| Hail | Very Low | 0.21 / yr | $140K |
| Drought | Very Low | 75.62 / yr | $10K |
| Tornado | Very Low | 0.13 / yr | $127K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Twin Falls County has received 4 federal disaster declarations since 2005, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Flood (1), Hurricane (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| April 2017 | Flood | Severe Winter Storms and Flooding |
| September 2005 | Hurricane | Hurricane Katrina |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Twin Falls County?
Twin Falls County has a composite FEMA National Risk Index score of 46.9 out of 100, placing it in the Low category and the 47th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Twin Falls County?
The three highest-rated hazards are Winter Weather (High, $779K EAL), Wildfire (Medium, $3M EAL), Landslide (Medium, $95K EAL). These account for most of the county's expected annual losses.
How does Twin Falls County compare to other Idaho counties?
Twin Falls County ranks #17 of 44 Idaho counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Twin Falls County had?
FEMA records 4 federal disaster declarations for Twin Falls County since 2005, most often 2 for biological events and 1 for flood 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. Twin Falls County's $17M EAL is a statistical average, not a guarantee for any specific year or address.