Is St. Clair County, IL in a flood zone?
FEMA's National Risk Index puts St. Clair County's flood hazard at the 94.5th 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 1.8 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
St. Clair County is one of the counties where FEMA's own denominator for mandated flood-zone structures is missing, so no compliance rate is shown rather than a guessed one — the data quality guide covers how common this is. Across all residential structures in St. Clair County, not just the ones FEMA mandates, 1% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
St. Clair County against the rest of the country
St. Clair County sits at rank 188 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 292 of 3144 by population (1 is biggest). St. Clair County, Illinois covers 657.748 square miles and counts roughly 251,149 residents.
Your street may differ from St. Clair County's average
FEMA counts 101,953 residential structures in St. Clair County overall, 1,007 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed St. Clair County's numbers. See the data quality guide for why St. Clair County, like hundreds of other counties, doesn't get a clean compliance percentage.