Thunder Lake

On the scoring rubric Thunder Lake grades a D: clarity at 5.0 ft and phosphorus readings still being added keep it in the lower bracket for Oneida County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

At a TSI of 54, Thunder Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of just 9 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. Thunder Lake covers 1,794 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Within the 134 graded lakes of Oneida County, Thunder Lake sits at rank 104, near the bottom of the county list.

Thunder Lake has at least one documented invasive species (Banded Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Walleye are documented at Thunder Lake, one of 4 fish species on record for the lake. Public access is available — the lake is on the Wisconsin DNR public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.