Holly Lake

On the scoring rubric Holly Lake grades a D: clarity at 4.9 ft and phosphorus readings still being added keep it in the lower bracket for Cook County.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. Holly Lake is a shallow lake at 6 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. The lake is compact at 76 acres, with 1.8 miles of shoreline and little volume to buffer nutrient inputs. Within the 128 graded lakes of Cook County, Holly Lake sits at rank 103, near the bottom of the county list.

Holly Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Walleye are documented at Holly Lake, one of 5 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a partial ice record — 5 observed ice-outs, centered near May 8. 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.