Is Yellowstone County, MT in a flood zone?
FEMA's National Risk Index puts Yellowstone County's flood hazard at the 84.5th percentile nationally — a middling flood hazard by national standards — driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 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 Yellowstone County
Homes with a federally backed mortgage inside Yellowstone County's mapped high-risk flood zone (the Special Flood Hazard Area, or SFHA) are legally required to carry an NFIP flood policy. In practice, 16.8% of them do — 147 active policies against 876 structures FEMA counts in that zone, leaving a real compliance gap. Across all residential structures in Yellowstone County, not just the ones FEMA mandates, 0.4% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Where Yellowstone County ranks
Yellowstone County sits at rank 511 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 407 of 3144 by population (1 is biggest). Yellowstone County, Montana is home to about 171,583 people across 2,633.402 square miles of land.
Your street may differ from Yellowstone County's average
FEMA counts 64,244 residential structures in Yellowstone County overall, 233 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Yellowstone County's numbers. The guide to what the Special Flood Hazard Area actually means explains why the mandatory-insurance rule exists and who it applies to.