Jefferson County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
Very LowComposite Risk Score
National percentile: 40th
Jefferson County faces very low composite natural disaster risk (NRI Risk Index score 40.1, 40th national percentile), driven primarily by winter weather and cold wave exposure. Expected annual loss across all 18 hazard types is $17M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Jefferson County at very low composite risk, with a National Risk Index score of 40.1 out of 100 — placing it in the 40th 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.
Most of Jefferson County's expected losses come from winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $329K in expected annual loss and about 13.69 events per year; cold wave (prolonged spells of dangerously low temperatures) at Medium risk — $6M in expected annual loss and about 2.56 events per year; and earthquake (ground shaking from sudden movement along geologic faults) at Low risk — $2M in expected annual loss and about 0.01 events per year. Across all hazards, FEMA estimates $17M in expected annual loss for a population of 31K.
Beyond physical exposure, Jefferson County has a very low social vulnerability rating (how susceptible the population is to harm) and a 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: Jefferson County has received 6 federal disaster declarations since 1976, including 2 for biological events and 2 for flood events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Jefferson County ranks #21 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | Medium | 13.69 / yr | $329K |
| Cold Wave | Medium | 2.56 / yr | $6M |
| Earthquake | Low | 0.01 / yr | $2M |
| Heat Wave | Medium | 1.94 / yr | $2M |
| Wildfire | Very Low | 0.00 / yr | $138K |
| Volcanic Activity | Very Low | 0.00 / yr | $37 |
| Lightning | Low | 30.94 / yr | $381K |
| Riverine Flood | Low | 0.39 / yr | $6M |
| Landslide | Very Low | 0.22 / yr | $596 |
| Drought | Very Low | 58.68 / yr | $9K |
| Hail | Very Low | 0.36 / yr | $100K |
| Strong Wind | Very Low | 0.90 / yr | $133K |
| Ice Storm | Very Low | 0.01 / yr | $8K |
| Tornado | Very Low | 0.12 / yr | $47K |
| Avalanche | Very Low | 0.01 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Jefferson County has received 6 federal disaster declarations since 1976, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Flood (2), 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 |
| June 1997 | Severe Storm | Severe Storms, Snowmelt, Land/Mud Slides, Flooding |
| June 1976 | Flood | Dam Collapse, Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Jefferson County?
Jefferson County has a composite FEMA National Risk Index score of 40.1 out of 100, placing it in the Very Low category and the 40th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Jefferson County?
The three highest-rated hazards are Winter Weather (Medium, $329K EAL), Cold Wave (Medium, $6M EAL), Earthquake (Low, $2M EAL). These account for most of the county's expected annual losses.
How does Jefferson County compare to other Idaho counties?
Jefferson County ranks #21 of 44 Idaho counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Jefferson County had?
FEMA records 6 federal disaster declarations for Jefferson County since 1976, most often 2 for biological events and 2 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. Jefferson County's $17M EAL is a statistical average, not a guarantee for any specific year or address.