McHenry County, IL: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, McHenry County scores at the 93.1th 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 1.1 times a year. This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
McHenry County's flood-insurance compliance gap
19.4% of the homes FEMA requires to carry flood insurance in McHenry County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 625 policies against 3,218 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Looking beyond the mandated zone, 0.7% of all residential structures in McHenry County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where McHenry County ranks
Among the 3144 US counties FEMA scores for flood hazard, McHenry County ranks 233 — 1 being the highest hazard nationally — and 234 by population among all 3144 counties covered here, where 1 is the largest. McHenry County, Illinois is home to about 315,959 people across 603.403 square miles of land.
What to do next if you own or are buying in McHenry County
FEMA counts 112,809 residential structures in McHenry County overall, 764 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
Where McHenry 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.