North Twin Lake

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

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. At 60 ft of maximum depth, North Twin Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. With 2,871 acres of surface and partial shoreline records, North Twin Lake is a large water by Wisconsin standards — recreational pressure is spread across a long shoreline. Among the 191 graded lakes in Vilas County, North Twin Lake sits at rank 90, above the county median.

Eurasian watermilfoil is established at North Twin Lake, which can dampen recreational access and pressure the native plant community. The fishery includes walleye alongside the lake's other 5 documented species — a notable draw for Wisconsin anglers. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.