How much flood risk does Mason County actually carry?
Mason County lands at the 79.3th percentile of FEMA's National Risk Index for flooding, "Relatively Moderate" territory — a middling flood hazard by national standards — with the hazard split between inland river flooding (about once every 6 years) and coastal storm surge (about 3.1 times a year). County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Mandatory flood insurance compliance in Mason County
21.9% of the homes FEMA requires to carry flood insurance in Mason County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 343 policies against 1,564 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Across all residential structures in Mason County, not just the ones FEMA mandates, 1.2% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
How Mason County compares nationally
Mason County sits at rank 681 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 791 of 3144 by population (1 is biggest). Mason County, Washington is home to about 69,632 people across 959.565 square miles of land.
What to do next if you own or are buying in Mason County
419 of Mason County's 35,251 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Mason County's numbers. Because storm surge plays a real role here, the guide to coastal vs. inland flood hazard is worth reading alongside this page.