Thomas Lake

On the LakeGrade scale Thomas Lake grades a B, with clarity at 14.0 ft and phosphorus readings still being added placing it above the Minnesota median.

A TSI value of 39 puts Thomas Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Thomas Lake is unusually deep for Minnesota at 110 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 1,465 acres, Thomas Lake is one of the larger lakes in Lake County, with 26.2 miles of shoreline supporting multiple distinct use patterns. Thomas Lake ranks 40 of 142 in Lake County — solidly in the upper half of the local distribution.

No invasive species are currently listed at Thomas Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Thomas Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.