Mercer Island, Washington: natural disaster risk
How exposed Mercer Island is to floods, storms and other hazards, from FEMA and NOAA records for King County.
Mercer Island is a city of 25,307 people in King County, Washington. FEMA's National Risk Index rates King County very high for natural hazards overall, higher than most of the US. The costliest hazards there are earthquake, inland flooding and heat wave, with about $1.7 billion in expected losses a year across the county. The weather service has logged 72 storm reports in the county since 1956, including 5 tornadoes and 8 floods. About 0.8% of homes in the county carry federal flood insurance.
Risk figures are for King County. FEMA National Risk Index December 2025; NOAA Storm Events; US Census Bureau ACS 2020 to 2024. Updated November 6, 2026.
Top risks in Mercer Island
Full King County report ›- Ask whether an older house is bolted to its foundation.
- Consider separate earthquake insurance where risk is high.
- Check the FEMA flood map for your address, and ask the seller or landlord about past flooding.
- Price a flood policy now. Most new federal policies take 30 days to start.
- Check that cooling works before summer.
- Know where the nearest cooling center is.
All hazards
| Hazard | Rating | A year |
|---|---|---|
| Earthquake | $1.2B | |
| Inland flooding | $417M | |
| Heat wave | $19M | |
| Avalanche | $11M | |
| Tsunami | $6M | |
| Tornado | $4M | |
| Volcanic activity | $2M | |
| Landslide | $2M | |
| Coastal flooding | $1M | |
| Ice storm | $1M | |
| Winter weather | $815K | |
| Lightning | $750K |
Homes in Mercer Island
Older homes and mobile homes usually take more damage in storms, floods and earthquakes. Ask about roof age, flood history and retrofits before you buy or rent.
Strongest tornadoes in King County
More cities in King County
Other cities in Washington
All ›Common questions about Mercer Island
Is Mercer Island safe from natural disasters?
Mercer Island is in King County, which FEMA's National Risk Index rates very high overall, higher than most of the US. The biggest hazards are earthquake, inland flooding, heat wave. No place is free of risk, so check the flood map and insurance for any home you consider.
What natural disasters happen in Mercer Island?
By expected yearly losses in King County, the top hazards are earthquake (Very High), inland flooding (Very High), heat wave (High). King County has been part of 33 federal disaster or emergency declarations for natural events.
Does Mercer Island get tornadoes?
Yes. NOAA records list 5 tornadoes in King County since 1950; the strongest was an F3 tornado on December 12, 1969. FEMA rates tornado risk in the county moderate.
Do I need flood insurance in Mercer Island?
Standard home insurance does not cover floods. In King County, about 0.8% of homes have federal flood insurance, and FEMA rates inland flooding risk very high. Check the FEMA flood map for your address and get a quote even outside a high-risk zone.