Sierra County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
Very LowComposite Risk Score
National percentile: 32th
Sierra County faces very low composite natural disaster risk (NRI Risk Index score 31.5, 32th national percentile), driven primarily by wildfire and landslide exposure. Expected annual loss across all 18 hazard types is $8M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Sierra County at very low composite risk, with a National Risk Index score of 31.5 out of 100 — placing it in the 32nd 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.
Risk here concentrates in 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; landslide (downhill movement of rock, soil, and debris on unstable slopes) at Medium risk — $97K in expected annual loss and about 3.01 events per year; and lightning (electrical discharges from storms that ignite fires and cause casualties) at Medium risk — $538K in expected annual loss and about 15.88 events per year. Across all hazards, FEMA estimates $8M in expected annual loss for a population of 3K.
Beyond physical exposure, Sierra County has a high 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). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
History supports the rating: Sierra County has received 16 federal disaster declarations since 1964, including 6 for flood events and 5 for severe storm events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides (severe storm), declared in April 2023.
Among 58 California counties, Sierra County ranks #57 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Wildfire | Medium | 0.02 / yr | $3M |
| Landslide | Medium | 3.01 / yr | $97K |
| Lightning | Medium | 15.88 / yr | $538K |
| Earthquake | Low | 0.04 / yr | $552K |
| Volcanic Activity | Very Low | 0.00 / yr | $8 |
| Avalanche | Very Low | 0.03 / yr | $303 |
| Riverine Flood | Low | 0.14 / yr | $4M |
| Drought | Low | 70.94 / yr | $37K |
| Winter Weather | Low | 36.59 / yr | $29K |
| Heat Wave | Very Low | 2.28 / yr | $9K |
| Hail | Very Low | 0.17 / yr | $6K |
| Strong Wind | Very Low | 0.11 / yr | $10K |
| Tornado | Very Low | 0.06 / yr | $4K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Sierra County has received 16 federal disaster declarations since 1964, most recently Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides in April 2023. Most frequent causes: Flood (6), Severe Storm (5), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2023 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| March 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| August 2020 | Fire | Wildfires |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| April 2017 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| February 2017 | Severe Storm | Severe Winter Storms, Flooding, and Mudslides |
| February 2006 | Severe Storm | Severe Storms, Flooding, Mudslides, and Landslides |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| January 1997 | Severe Storm | Severe Storms, Flooding, Mud and Landslides |
Showing the 10 most recent of 16 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Sierra County?
Sierra County has a composite FEMA National Risk Index score of 31.5 out of 100, placing it in the Very Low category and the 32th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Sierra County?
The three highest-rated hazards are Wildfire (Medium, $3M EAL), Landslide (Medium, $97K EAL), Lightning (Medium, $538K EAL). These account for most of the county's expected annual losses.
How does Sierra County compare to other California counties?
Sierra County ranks #57 of 58 California counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Sierra County had?
FEMA records 16 federal disaster declarations for Sierra County since 1964, most often 6 for flood events and 5 for severe storm events. The most recent was Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared in April 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. Sierra County's $8M EAL is a statistical average, not a guarantee for any specific year or address.