Mercer Island, WA
Local storm history & FEMA National Risk Index data
Mercer Island is rated Very High for overall natural hazard risk — among the most at-risk counties in the country — based on FEMA's National Risk Index for King County, WA. The county's highest-rated hazards are earthquake, inland flooding, and avalanche.
Storm events near Mercer Island
NOAA-recorded tornado, hail, and flood events within 25 miles of Mercer Island's center, 2016–2026 — the only hazards NOAA reports with exact coordinates, so these counts are specific to Mercer Island itself, not the whole county.
County-wide hazard risk
Every other hazard FEMA and NOAA track — including drought — is only scored at the county level. These are King County's FEMA National Risk Index scores, covering Mercer Island along with the rest of the county, not a Mercer Island-specific figure.
| Hazard | NRI score | Rating |
|---|---|---|
| Wildfire | 79.5 | Relatively Low |
| Inland Flooding | 99.5 | Very High |
| Coastal Flooding | 71 | Relatively Moderate |
| Earthquake | 99.9 | Very High |
| Heat Wave | 98.2 | Relatively High |
| Tornado | 73.2 | Relatively Moderate |
| Avalanche | 99.3 | Very High |
| Cold Wave | 26.5 | Relatively Low |
| Drought | 13.7 | Very Low |
| Hail | 3.1 | Very Low |
| Hurricane | — | Not Applicable |
| Ice Storm | 91.1 | Relatively High |
| Landslide | 99 | Relatively High |
| Lightning | 74.7 | Relatively Moderate |
| Strong Wind | 4.5 | Very Low |
| Tsunami | 67.7 | Relatively Low |
| Volcanic Activity | 97.4 | Relatively High |
| Winter Weather | 94.7 | Relatively High |
Source: FEMA National Risk Index v1.20.0, December 2025. See the methodology page for definitions, or the full King County risk profile for disaster declarations, social vulnerability, and climate projection data.
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Frequently asked questions
What natural hazards is Mercer Island, WA at risk of?
Mercer Island is rated Very High for overall natural hazard risk by FEMA's National Risk Index — among the most at-risk counties in the country. The highest-rated hazards for King County, where Mercer Island is located, are earthquake, inland flooding, and avalanche.
What is Mercer Island's biggest natural hazard risk?
Earthquake is the highest-rated hazard for King County, where Mercer Island is located, scoring 99.9 out of 100 on FEMA's National Risk Index (rated "Very High").
Is Mercer Island a high-risk area for natural disasters?
Yes — Mercer Island carries among the most at-risk counties in the country for overall natural hazard risk, per FEMA's National Risk Index rating of "Very High" for King County.
Has Mercer Island had tornadoes, hail, or flooding?
NOAA has recorded 1 tornado, 1 inland flooding events within 25 miles of Mercer Island since 2016.