Day County, SD flood risk explained
Flood hazard in Day County sits at the 20th national percentile, among the lowest flood hazard in the country; 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. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Mandatory flood insurance compliance in Day County
FEMA hasn't published a residential structure count for Day County's mapped flood zone, so a reliable mandatory-compliance percentage can't be computed here — see the data quality guide for why this gap exists for roughly a quarter of US counties. Looking beyond the mandated zone, 0.3% of all residential structures in Day County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where Day County ranks
Among the 3144 US counties FEMA scores for flood hazard, Day County ranks 2557 — 1 being the highest hazard nationally — and 2788 by population among all 3144 counties covered here, where 1 is the largest. Day County, South Dakota is home to about 5,408 people across 1,028.49 square miles of land.
Your street may differ from Day County's average
Across all of Day County's 4,240 residential structures, 12 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where Day County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. Day 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.