Is Jefferson County, CO in a flood zone?
FEMA's National Risk Index puts Jefferson County's flood hazard at the 93.4th percentile nationally — well above the national norm for flood hazard — driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 1.3 times a year. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Who actually carries the flood insurance FEMA requires
40.9% of the homes FEMA requires to carry flood insurance in Jefferson County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 728 policies against 1,778 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Across all residential structures in Jefferson County, not just the ones FEMA mandates, 0.6% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Jefferson County against the rest of the country
Jefferson County sits at rank 222 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 123 of 3144 by population (1 is biggest). Jefferson County, Colorado covers 764.424 square miles and counts roughly 578,533 residents.
What to do next if you own or are buying in Jefferson County
Across all of Jefferson County's 205,607 residential structures, 1,293 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 Jefferson 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.