Jefferson County, ID: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, Jefferson County scores at the 37.1th percentile for flood hazard, rated "Relatively Low" — below the national norm for flood hazard. The hazard here is driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about once every 3 years. This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
Mandatory flood insurance compliance in Jefferson County
Homes with a federally backed mortgage inside Jefferson 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, 5.8% of them do — 23 active policies against 398 structures FEMA counts in that zone, leaving a real compliance gap. Looking beyond the mandated zone, 0.3% of all residential structures in Jefferson County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where Jefferson County ranks
Among the 3144 US counties FEMA scores for flood hazard, Jefferson County ranks 2042 — 1 being the highest hazard nationally — and 1317 by population among all 3144 counties covered here, where 1 is the largest. About 34,854 people live in Jefferson County, Idaho, spread over 1,093.681 square miles.
Your street may differ from Jefferson County's average
35 of Jefferson County's 12,119 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
Where Jefferson County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. If you're unsure why any of this insurance requirement exists at all, the SFHA explainer covers it from first principles.