Polly Lake

Polly Lake earns a D — measurements through 2024 show persistent nutrient pressure that limits clarity through the summer. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

At a TSI of 55, Polly Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Polly Lake reaches 21 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 485 acres, Polly Lake fits the Minnesota median for monitored lakes, with 18.6 miles of shoreline. Within the 142 graded lakes of Lake County, Polly Lake sits at rank 127, near the bottom of the county list.

No invasive species are currently listed at Polly Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Polly Lake, one of 8 fish species on record for the lake. No formal public access is documented at Polly Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.