Iosco County Lake Quality

There are 31 monitored lakes in Iosco County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. With an average grade of B, Iosco County sits comfortably above the Michigan median.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Long Lake (A) is the cleanest in the county.