Jefferson County, NY: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, Jefferson County scores at the 78th percentile for flood hazard, rated "Relatively Moderate" — a middling flood hazard by national standards. 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 1 years. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Jefferson County's flood-insurance compliance gap
FEMA's own figures for Jefferson County report more NFIP policies in the mapped flood zone than FEMA's own count of residential structures there, which produces a compliance rate over 100% — a data problem on FEMA's side, not evidence that everyone here is over-insured. See the data quality guide for how widespread this is. Looking beyond the mandated zone, 0.6% 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 721 — 1 being the highest hazard nationally — and 565 by population among all 3144 counties covered here, where 1 is the largest. About 113,140 people live in Jefferson County, New York, spread over 1,267.932 square miles.
Checking a specific address in Jefferson County
FEMA counts 45,113 residential structures in Jefferson County overall, 253 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
Where Jefferson County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. Jefferson County's compliance figure is one of the ones affected by FEMA's incomplete denominator data — the data quality guide explains what that means and how many counties it touches.