Lewis County, Washington Natural Disaster Risk
FEMA National Risk Index assessment · WA
MediumComposite Risk Score
National percentile: 90th
Lewis County faces medium composite natural disaster risk (NRI Risk Index score 89.7, 90th national percentile), driven primarily by earthquake and landslide exposure. Expected annual loss across all 18 hazard types is $71M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Lewis County at medium composite risk, with a National Risk Index score of 89.7 out of 100 — placing it in the 90th national percentile and near the national midpoint for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Lewis County's expected losses come from earthquake (ground shaking from sudden movement along geologic faults) at Medium risk — $30M 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 — $195K in expected annual loss and about 5.75 events per year; and volcanic activity (eruptions producing ashfall, lava, and pyroclastic hazards) at Medium risk — $287K in expected annual loss and about 0.01 events per year. Across all hazards, FEMA estimates $71M in expected annual loss for a population of 82K.
Beyond physical exposure, Lewis County has a medium 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: Lewis County has received 37 federal disaster declarations since 1964, including 19 for flood events and 13 for severe storm events. The most recent was Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides (flood), declared in April 2026.
Among 39 Washington counties, Lewis County ranks #15 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | Medium | 0.02 / yr | $30M |
| Landslide | Medium | 5.75 / yr | $195K |
| Volcanic Activity | Medium | 0.01 / yr | $287K |
| Riverine Flood | Medium | 0.29 / yr | $37M |
| Avalanche | High | 0.70 / yr | $1M |
| Heat Wave | Low | 3.24 / yr | $1M |
| Wildfire | Low | 0.00 / yr | $263K |
| Winter Weather | Low | 29.26 / yr | $40K |
| Ice Storm | Low | 0.51 / yr | $37K |
| Lightning | Low | 6.58 / yr | $103K |
| Strong Wind | Low | 0.02 / yr | $168K |
| Tornado | Very Low | 0.14 / yr | $162K |
| Drought | Very Low | 2.62 / yr | $46 |
| Hail | Very Low | 0.03 / yr | $12K |
| Cold Wave | Very Low | 0.00 / yr | $149 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Lewis County has received 37 federal disaster declarations since 1964, most recently Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides in April 2026. Most frequent causes: Flood (19), Severe Storm (13), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| April 2026 | Flood | Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| December 2025 | Flood | Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| April 2024 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| January 2023 | Severe Storm | Severe Winter Storm, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| March 2022 | Flood | Severe Winter Storms, Snowstorms, Straight-Line Winds, Flooding |
| January 2022 | Flood | Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| April 2021 | Severe Storm | Severe Winter Storm, Straight-Line Winds, Flooding, Landslides, and Mudslides |
| April 2020 | Flood | Severe Storms, Flooding, Landslides, and Mudslides |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
Showing the 10 most recent of 37 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Lewis County?
Lewis County has a composite FEMA National Risk Index score of 89.7 out of 100, placing it in the Medium category and the 90th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Lewis County?
The three highest-rated hazards are Earthquake (Medium, $30M EAL), Landslide (Medium, $195K EAL), Volcanic Activity (Medium, $287K EAL). These account for most of the county's expected annual losses.
How does Lewis County compare to other Washington counties?
Lewis County ranks #15 of 39 Washington counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Lewis County had?
FEMA records 37 federal disaster declarations for Lewis County since 1964, most often 19 for flood events and 13 for severe storm events. The most recent was Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides, declared in April 2026.
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. Lewis County's $71M EAL is a statistical average, not a guarantee for any specific year or address.