Grade C Lakes, Fair

581 lakes (15% of all graded lakes)

C is the largest bracket on the rubric for many states: productive, swimmable most days, with the occasional July week where blooms make the water unappealing. 581 lakes grade C.

Eutrophic conditions dominate, with the bracket reflecting the algal pressure that comes from elevated phosphorus and the right summer temperatures. About 13% of the C-grade bracket is deep lakes, with the remainder shallow. Depth helps but does not guarantee a grade — watershed land use does most of the heavy lifting.

A B C D F

581

Total Lakes

453

Minnesota

128

Wisconsin

Lake	County	State	Clarity	Depth	Fish
Round Lake	Hennepin	MN	7.4 ft	37 ft	8
Horseshoe Lake	Chisago	MN	4.6 ft	53 ft	14
Schram Lake	Beltrami	MN	3.9 ft	-	0
Green Lake	Chisago	MN	6 ft	32 ft	15
George Lake	Anoka	MN	7.3 ft	32 ft	12
North Lake 2	Goodhue	MN	123.5 ft	-	0
Coon Lake	Anoka	MN	5.6 ft	27 ft	14
Mcdonough Lake	Dakota	MN	9.8 ft	13 ft	4
Perch Lake	Carlton	MN	4.9 ft	-	0
Jensen Lake	Dakota	MN	5 ft	-	0
Jaskari Lake	Carlton	MN	6.4 ft	-	0
Kroon Lake	Chisago	MN	5.9 ft	30 ft	13
Rice Portage Lake	Carlton	MN	1.3 ft	-	0
Turtle Lake Deep	Cook	MN	-324.8 ft	-	0
Sturgeon Lake 2	Goodhue	MN	134.5 ft	-	0
Middle Pigeon Lake	Itasca	MN	7.5 ft	-	0
Fannie Lake	Isanti	MN	7 ft	33 ft	13
Teal Lake Deep	Cook	MN	3.3 ft	-	0
Cut Foot Sioux Lake	Itasca	MN	7.5 ft	-	0
Namakan Lake	St. Louis	MN	8.2 ft	150 ft	18
Rainy Lake	St. Louis	MN	9.5 ft	161 ft	17
Sand Point Lake	St. Louis	MN	7.5 ft	184 ft	21
Oslo Lake	St. Louis	MN	9.2 ft	36 ft	2
Namakan Lake	St. Louis	MN	9.8 ft	150 ft	18
Jorgens Lake	St. Louis	MN	7.2 ft	21 ft	3
Rainy Lake	St. Louis	MN	7.2 ft	161 ft	17
War Club Lake	St. Louis	MN	7.9 ft	40 ft	8
Clearwater Lake	Itasca	MN	9.5 ft	16 ft	0
Mud Lake	Wright	MN	5.6 ft	65 ft	15
Pelican Lake	St. Louis	MN	7.5 ft	38 ft	11
Birch Lake	Ramsey	MN	5.9 ft	-	0
Birch Lake	Sherburne	MN	5.8 ft	18 ft	13
Birch Lake	St. Louis	MN	3.9 ft	25 ft	10
Round Lake	Ramsey	MN	8.2 ft	-	0
Round Lake	Itasca	MN	7.5 ft	16 ft	0
Horseshoe Lake	Cook	MN	7 ft	26 ft	0
Horseshoe Lake	Lake	MN	8 ft	40 ft	0
Stark Lake	Crow Wing	MN	8 ft	66 ft	10
Long Lake	Washington	MN	8.5 ft	25 ft	0
Long Lake	Itasca	MN	7.3 ft	34 ft	14
Long Lake	Meeker	MN	7.5 ft	28 ft	12
Big Swan Lake	Todd	MN	8.9 ft	45 ft	16
Unnamed Lake	Morrison	MN	6.9 ft	-	0
Unnamed Lake	Itasca	MN	7.9 ft	-	0
Unnamed Lake	St. Louis	MN	4.8 ft	7 ft	6
Unnamed Lake	Grant	MN	6.7 ft	-	0
Unnamed Lake	Otter Tail	MN	3.9 ft	-	0
Unnamed Lake	Brown	MN	0.3 ft	-	0
Maple Lake	Wright	MN	9 ft	-	0
Stella Lake	Meeker	MN	7.5 ft	75 ft	15
Chippewa Lake	Lake	MN	7 ft	-	0
Twin Lake	Ramsey	MN	7.9 ft	33 ft	8
Bryant Lake	Hennepin	MN	9.8 ft	45 ft	11
Marion Lake	Dakota	MN	7 ft	21 ft	14
Wind Lake	Lake	MN	9 ft	32 ft	10
Elms Lake	Isanti	MN	6.9 ft	26 ft	13
Blue Lake	Isanti	MN	8.9 ft	31 ft	13
Eagle Lake	Carlton	MN	7 ft	35 ft	12
Eagle Lake	Kandiyohi	MN	6.4 ft	67 ft	17
Auburn Lake	Carver	MN	7.2 ft	84 ft	14
Colby Lake	St. Louis	MN	3.5 ft	30 ft	15
Johanna Lake	Ramsey	MN	7.2 ft	43 ft	13
Fish Lake	Dakota	MN	6.9 ft	33.5 ft	7
Sand Lake	St. Louis	MN	9 ft	15 ft	9
Sand Lake	Carlton	MN	5 ft	27 ft	3
West Vermilion Lake	St. Louis	MN	7.9 ft	76 ft	17
Beaver Lake	Ramsey	MN	7.9 ft	11 ft	7
Battle Creek Lake	Washington	MN	7.4 ft	15.3 ft	10
Norway Lake	Cass	MN	6.6 ft	12 ft	14
Union Lake	Wright	MN	5.5 ft	35 ft	15
Union Lake	Rice	MN	3 ft	10 ft	0
Florence Lake	Isanti	MN	9 ft	26 ft	15
Gibson Lake	Lake	MN	8.5 ft	24 ft	0
Leech Lake	Cass	MN	9 ft	-	0
Bass Lake	Pine	MN	8.3 ft	24 ft	9
Island Lake	Pine	MN	7 ft	42 ft	13
Island Lake	Itasca	MN	8.9 ft	35 ft	15
Rossman Lake	Becker	MN	7.5 ft	20 ft	12
Moose Lake	Todd	MN	7 ft	26 ft	13
Rainy Lake	Koochiching	MN	7.5 ft	161 ft	17
Crooked Lake	Lake	MN	9 ft	165 ft	0
Portage Lake	Hubbard	MN	5.7 ft	17 ft	12
Mille Lacs Lake	Mille Lacs	MN	9 ft	42 ft	21
Cedar Lake	Aitkin	MN	8.8 ft	18 ft	9
Carp Lake	Unknown	MN	8.8 ft	34 ft	10
Turtle Lake	Crow Wing	MN	8 ft	33 ft	8
Fairy Lake	St. Louis	MN	7 ft	19 ft	0
Gull Lake	Beltrami	MN	5.9 ft	23 ft	13
Koronis Lake	Stearns	MN	6 ft	132 ft	22
Dode Lake	Itasca	MN	7.3 ft	25 ft	0
Devil'S Lake	Kanabec	MN	7.3 ft	19 ft	0
Lewis Lake	Kanabec	MN	7 ft	48 ft	11
Silver Lake	Ramsey	MN	7 ft	18 ft	12
Caribou Lake	Cook	MN	8 ft	26 ft	0
Goose Lake	Chisago	MN	4.5 ft	55 ft	15
Roy Lake	Mahnomen	MN	6 ft	16 ft	13
Rock Lake	Wright	MN	7.5 ft	37 ft	15
Rock Lake	Cass	MN	5.9 ft	17 ft	11
Green Prairie Fish Lake	Morrison	MN	8 ft	22 ft	14
Rice Marsh Lake	Hennepin	MN	7.7 ft	-	0

Showing 100 of 581 Grade C lakes.

Frequently Asked Questions

How many lakes have a grade of C?

There are 581 Grade C (Fair) lakes in Minnesota and Wisconsin, 453 in Minnesota and 128 in Wisconsin. This represents 15% of all graded lakes.

What does a Grade C mean?

Grade C means fair water quality with moderate clarity (7-10 ft visibility), moderate phosphorus, and some algae presence. Generally safe for swimming but algae blooms possible in summer.

Source: EPA National Aquatic Resource Surveys, 2026.