Is Hillsborough County, NH in a flood zone?
FEMA's National Risk Index puts Hillsborough County's flood hazard at the 92.6th 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 1.7 times a year. This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
Who actually carries the flood insurance FEMA requires
Homes with a federally backed mortgage inside Hillsborough 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, 34.5% of them do — 439 active policies against 1,273 structures FEMA counts in that zone, leaving a real compliance gap. Across all residential structures in Hillsborough County, not just the ones FEMA mandates, 0.7% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Hillsborough County against the rest of the country
Hillsborough County sits at rank 249 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 175 of 3144 by population (1 is biggest). Hillsborough County, New Hampshire is home to about 430,462 people across 876.53 square miles of land.
What to do next if you own or are buying in Hillsborough County
Across all of Hillsborough County's 106,435 residential structures, 751 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 Hillsborough 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.