It is a 7,314 acre lake with a maximum depth of 126 feet and clear water. There are several relatively minor inlets, located mostly on the north side of the lake. The Shagawa River is the only outlet which flows out of the southwest corner of the lake where it then turns and heads east to Shagawa Lake. Burntside Lake is a two-story fishery with deep, cold, well oxygenated water capable of supporting a cold water fishery (fish such as lake trout, lake whitefish, cisco and burbot) and a shallow, warmer, but still well oxygenated area capable of supporting a cool and warm water fishery (fish such as walleye, northern pike, bass and panfish).
Lake bottom substrates along the shoreline are mostly boulder and ledgerock. Some bays have soft bottoms with a fair amount of aquatic vegetation. Additionally, a few bays are quite sandy and make for great swimming areas. Burntside has a long history of stocking dating back to 1912. Since 1965, walleye and lake trout were the only species that were stocked. Lake trout were stocked from the 1990's to 2010. Walleye fingerlings are still currently being stocked in even years at around 25,000 fish per stocking.