Rainy Lake

Rainy Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 53, Rainy Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake's 161 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. At 210,200 acres, Rainy Lake is one of the larger lakes in Koochiching County, with 2176.3 miles of shoreline supporting multiple distinct use patterns. Rainy Lake ranks 7 of 7 in Koochiching County — at the lower end of the locally monitored distribution.

Zebra mussel presence at Rainy Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Walleye are documented at Rainy Lake, one of 17 fish species on record for the lake. A documented public access point at Rainy Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been logged at Rainy Lake more than two dozen times, putting the median around May 4 — a useful baseline for tracking climate trends. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.