How much flood risk does Petroleum County actually carry?
Petroleum County lands at the 2th percentile of FEMA's National Risk Index for flooding, "Very Low" territory — among the lowest flood hazard in the country — with the hazard driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about once every 1 years. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Mandatory flood insurance compliance in Petroleum County
Homes with a federally backed mortgage inside Petroleum 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, 50% of them do — 1 active policies against 2 structures FEMA counts in that zone, leaving a real compliance gap. Across all residential structures in Petroleum County, not just the ones FEMA mandates, 0.2% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Petroleum County against the rest of the country
Petroleum County sits at rank 3087 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 3137 of 3144 by population (1 is biggest). About 525 people live in Petroleum County, Montana, spread over 1,655.625 square miles.
Your street may differ from Petroleum County's average
Across all of Petroleum County's 636 residential structures, 1 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Petroleum 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.