Top counties by volcanic activity risk
Volcanic activity risk reflects expected losses from lava flows, tephra fall, lahars (volcanic mudflows), and volcanic gases. The highest-risk counties are in Washington (Mt. Rainier), Oregon (Mt. Hood), and Hawaii (Kilauea, Mauna Loa). Alaska's Aleutian chain contains many active volcanoes affecting nearby communities and trans-Pacific air traffic. Volcanic ashfall events are reported at forecast-zone level in NOAA Storm Events and are not included in county-level counts.
| # | County | State | NRI score | Rating |
|---|---|---|---|---|
| 1 | Hawaii County | HI | 100 | Very High |
| 2 | Cowlitz County | WA | 99.7 | Relatively High |
| 3 | Pierce County | WA | 99.3 | Relatively High |
| 4 | Skagit County | WA | 99 | Relatively High |
| 5 | Aleutians West Census Area | AK | 98.7 | Relatively High |
| 6 | Maui County | HI | 98.4 | Relatively High |
| 7 | Siskiyou County | CA | 98 | Relatively High |
| 8 | Aleutians East Borough | AK | 97.7 | Relatively High |
| 9 | King County | WA | 97.4 | Relatively High |
| 10 | Skamania County | WA | 97.1 | Relatively High |
| 11 | Lake County | CA | 96.7 | Relatively Moderate |
| 12 | Snohomish County | WA | 96.4 | Relatively Moderate |
| 13 | Deschutes County | OR | 96.1 | Relatively Moderate |
| 14 | Clackamas County | OR | 95.8 | Relatively Moderate |
| 15 | Hood River County | OR | 95.4 | Relatively Moderate |
| 16 | Lewis County | WA | 95.1 | Relatively Moderate |
| 17 | Shasta County | CA | 94.8 | Relatively Moderate |
| 18 | Lane County | OR | 94.5 | Relatively Moderate |
| 19 | Thurston County | WA | 94.1 | Relatively Moderate |
| 20 | Sitka City and Borough | AK | 93.8 | Relatively Moderate |
| 21 | Multnomah County | OR | 93.5 | Relatively Moderate |
| 22 | Whatcom County | WA | 93.2 | Relatively Moderate |
| 23 | Marion County | OR | 92.8 | Relatively Moderate |
| 24 | Tehama County | CA | 92.5 | Relatively Low |
| 25 | Klickitat County | WA | 92.2 | Relatively Low |
| 26 | Linn County | OR | 91.9 | Relatively Low |
| 27 | Klamath County | OR | 91.5 | Relatively Low |
| 28 | Wasco County | OR | 91.2 | Relatively Low |
| 29 | Prince of Wales-Hyder Census Area | AK | 90.9 | Relatively Low |
| 30 | Chelan County | WA | 90.6 | Relatively Low |
| 31 | Lake and Peninsula Borough | AK | 90.2 | Relatively Low |
| 32 | Kenai Peninsula Borough | AK | 89.9 | Relatively Low |
| 33 | Nome Census Area | AK | 89.6 | Relatively Low |
| 34 | Washington County | OR | 89.3 | Relatively Low |
| 35 | Plumas County | CA | 88.9 | Relatively Low |
| 36 | Clark County | WA | 88.6 | Relatively Low |
| 37 | Mono County | CA | 88.3 | Relatively Low |
| 38 | Yakima County | WA | 87.9 | Relatively Low |
| 39 | Jefferson County | OR | 87.6 | Relatively Low |
| 40 | Anchorage Municipality | AK | 87.3 | Relatively Low |
| 41 | Lassen County | CA | 87 | Relatively Low |
| 42 | Churchill County | NV | 86.6 | Relatively Low |
| 43 | Petersburg Borough | AK | 86.3 | Relatively Low |
| 44 | Imperial County | CA | 86 | Relatively Low |
| 45 | Coconino County | AZ | 85.7 | Relatively Low |
| 46 | Douglas County | OR | 85.3 | Relatively Low |
| 47 | Sonoma County | CA | 85 | Relatively Low |
| 48 | Island County | WA | 84.7 | Relatively Low |
| 49 | Yamhill County | OR | 84.4 | Relatively Low |
| 50 | Polk County | OR | 84 | Very Low |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties — a score of 95 means this county's expected annual loss from volcanic activity exceeds 95% of all other counties. See the methodology page for definitions. Download the full CSV for all 307 scored counties.
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