Mason County, Washington Natural Disaster Risk
FEMA National Risk Index assessment · WA
MediumComposite Risk Score
National percentile: 85th
Mason County faces medium composite natural disaster risk (NRI Risk Index score 85.3, 85th national percentile), driven primarily by landslide and earthquake exposure. Expected annual loss across all 18 hazard types is $44M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Mason County is medium, with a National Risk Index score of 85.3 out of 100 — placing it in the 85th 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.
Risk here concentrates in landslide (downhill movement of rock, soil, and debris on unstable slopes) at High risk — $500K in expected annual loss and about 10.89 events per year; earthquake (ground shaking from sudden movement along geologic faults) at Medium risk — $26M in expected annual loss and about 0.03 events per year; and riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Medium risk — $15M in expected annual loss and about 0.18 events per year. Across all hazards, FEMA estimates $44M in expected annual loss for a population of 66K.
Beyond physical exposure, Mason 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: Mason County has received 32 federal disaster declarations since 1964, including 13 for severe storm events and 12 for flood events. The most recent was Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides (flood), declared in April 2026.
Among 39 Washington counties, Mason County ranks #20 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | High | 10.89 / yr | $500K |
| Earthquake | Medium | 0.03 / yr | $26M |
| Riverine Flood | Medium | 0.18 / yr | $15M |
| Coastal Flood | Medium | 3.15 / yr | $1M |
| Heat Wave | Low | 2.67 / yr | $653K |
| Volcanic Activity | Very Low | 0.00 / yr | $8 |
| Winter Weather | Low | 11.83 / yr | $47K |
| Wildfire | Very Low | 0.00 / yr | $26K |
| Tsunami | Very Low | 0.06 / yr | $433K |
| Avalanche | Very Low | 0.01 / yr | $225 |
| Ice Storm | Very Low | 0.31 / yr | $19K |
| Lightning | Very Low | 5.15 / yr | $54K |
| Tornado | Very Low | 0.04 / yr | $94K |
| Drought | Very Low | 1.27 / yr | $5 |
| Strong Wind | Very Low | 0.01 / yr | $33K |
| Hail | Very Low | 0.01 / yr | $4K |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
Disaster History
Mason County has received 32 federal disaster declarations since 1964, most recently Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides in April 2026. Most frequent causes: Severe Storm (13), Flood (12), 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 |
| July 2023 | Fire | Mcewan Fire |
| March 2022 | Flood | Severe Winter Storms, Snowstorms, Straight-Line Winds, Flooding |
| 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 |
| March 2019 | Severe Storm | Severe Winter Storms, Straight-Line Winds, Flooding, Landslides, Mudslides, Tornado |
Showing the 10 most recent of 32 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Mason County?
Mason County has a composite FEMA National Risk Index score of 85.3 out of 100, placing it in the Medium category and the 85th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Mason County?
The three highest-rated hazards are Landslide (High, $500K EAL), Earthquake (Medium, $26M EAL), Riverine Flood (Medium, $15M EAL). These account for most of the county's expected annual losses.
How does Mason County compare to other Washington counties?
Mason County ranks #20 of 39 Washington counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Mason County had?
FEMA records 32 federal disaster declarations for Mason County since 1964, most often 13 for severe storm events and 12 for flood 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. Mason County's $44M EAL is a statistical average, not a guarantee for any specific year or address.