Best Swimming Lakes in Minnesota
Not all lakes are created equal when it comes to swimming. Water quality varies dramatically, some lakes have crystal clear water with visibility exceeding 20 feet, while others are so murky you cannot see your hand below the surface. Here is how to use water quality data to find the best swimming lakes.
Looking for the best swimming lakes in a specific state? Jump straight to a state ranking of algae-safe, Grade A and B lakes: Minnesota · Wisconsin · Illinois · Michigan · Iowa · Ohio · Pennsylvania · New York · Missouri · Indiana · North Dakota · South Dakota · Florida · Colorado · North Carolina · Vermont · Texas · Oregon · Arkansas · Oklahoma · Kansas · Nebraska · Nevada · Arizona · Idaho · Montana · New Mexico · Tennessee · Alabama · Virginia · Kentucky · Utah · Washington · Wyoming · Georgia · Massachusetts · Ontario · Québec
How to Read Lake Grades for Swimming
LakeQuality assigns a nutrient-and-algae letter (A–F) from EPA ecoregion condition classes, and shows clarity separately. Use both when you pick a swimming lake:
- Water Clarity (Secchi Depth), measured in feet. Higher is better. You want at least 4-5 feet of visibility to see underwater hazards. Readings over 15 feet are exceptionally clear. Clarity is not the letter.
- Phosphorus, the nutrient that feeds algae. Lower is better. High phosphorus means more algae blooms, which can produce toxins harmful to humans and pets. The letter grades phosphorus against that lake's ecoregion, not a single national cutoff.
- Chlorophyll-a, directly measures algae in the water. Low single-digit µg/L usually means minimal algae. Above 20 µg/L means visible algae that may include harmful blue-green varieties.
Swimming Safety by Grade
| Grade | Swimming Assessment |
|---|---|
| A | Excellent, crystal clear water, minimal algae, ideal for swimming |
| B | Good, clear water, low algae, safe for swimming |
| C | Fair, moderate clarity, some algae may be present, generally safe |
| D | Nutrient-rich, murkier water, higher algae — check advisories before swimming |
| F | Algae-prone — skip the water if you see scum or a paint-like bloom; cabins and rentals still listed on the lake page |
Top 25 Lakes for Swimming
These lakes have the best water quality grades and are ideal for swimming and recreation:
| Rank | Lake | County | State | Grade | Clarity |
|---|---|---|---|---|---|
| 1 | Rainy Lake | Cass | MN | A | 13.9 ft |
| 2 | Crane Lake | Otter Tail | MN | A | 9 ft |
| 3 | Lobster Lake | Douglas | MN | A | 13 ft |
| 4 | East Fox Lake | Crow Wing | MN | A | 16.4 ft |
| 5 | Deep Portage Lake | Cass | MN | A | 15.4 ft |
| 6 | Clearwater Lake | Cook | MN | A | 29 ft |
| 7 | Clearwater Lake | Wright | MN | A | 9.8 ft |
| 8 | Clearwater Lake | Crow Wing | MN | A | 13 ft |
| 9 | Clearwater Lake | Clearwater | MN | A | 10 ft |
| 10 | Lower Hay Lake | Crow Wing | MN | A | 18.5 ft |
| 11 | Latoka Lake | Douglas | MN | A | 19 ft |
| 12 | Little Birch Lake | Todd | MN | A | 13 ft |
| 13 | North Long Lake | Crow Wing | MN | A | 15.1 ft |
| 14 | Bad Medicine Lake | Becker | MN | A | 25 ft |
| 15 | Mud Lake | Becker | MN | A | 12.5 ft |
| 16 | Big Lake | Beltrami | MN | A | 9.7 ft |
| 17 | Big Lake | Carlton | MN | A | 10 ft |
| 18 | Big Lake | Sherburne | MN | A | 13.6 ft |
| 19 | Big Lake | St. Louis | MN | A | 8.2 ft |
| 20 | Big Sugar Bush Lake | Becker | MN | A | 16.5 ft |
| 21 | Pelican Lake | Otter Tail | MN | A | 16.4 ft |
| 22 | Pelican Lake | Crow Wing | MN | A | 14.3 ft |
| 23 | Fullers Lake: East Basin | Beltrami | MN | A | 15 ft |
| 24 | Birch Lake | Ramsey | MN | A | 5.9 ft |
| 25 | Birch Lake | Wright | MN | A | 15 ft |
Blue-Green Algae Warning Signs
Even if a lake has a good historical grade, blue-green algae blooms can appear quickly during hot summer weather. Watch for these warning signs before entering the water:
- Water that looks like green paint or pea soup
- Floating green or blue-green mats on the surface
- A strong musty or earthy odor from the water
- Dead fish along the shoreline
- Signs posted by local health departments
If you see any of these signs, do not swim, wade, or let pets drink from the lake. Blue-green algae(cyanobacteria) can produce toxins that cause skin rashes, nausea, and in severe cases, liver damage.
Frequently Asked Questions
Is it safe to swim in Minnesota lakes?
Most Minnesota lakes are safe for swimming. Lakes graded A or B by LakeQuality have excellent to good water quality with clear water and low algae. Lakes graded D or F should be avoided due to high algae levels that may produce harmful toxins. Always check for local advisories before swimming.
How do I know if a lake has harmful algae?
Blue-green algae (cyanobacteria) blooms look like green paint, pea soup, or floating mats on the water surface. A high chlorophyll-a reading (above 20 µg/L) indicates significant algae. Lakes with a D or F grade for chlorophyll-a should be avoided for swimming.
What Secchi depth is safe for swimming?
A Secchi depth of 4 feet or more generally indicates water clear enough to see underwater hazards. Readings over 15 feet are exceptionally clear. Murky water with less than 3 feet of visibility hides hazards. Those bands describe visibility — they are not the A–F letter, and they are not a same-day clearance.
Are Wisconsin lakes safe to swim in?
Many Wisconsin lakes offer excellent swimming. The clearest lakes in Wisconsin have visibility exceeding 10-15 feet. Check individual lake grades on LakeQuality, A and B rated lakes are excellent for swimming.
Which states does this swimming ranking cover?
The ranking spans every state LakeQuality covers, currently 38 states: Minnesota, Wisconsin, Illinois, Michigan, Iowa, Ohio, Pennsylvania, New York, Missouri, Indiana, North Dakota, South Dakota, Florida, Colorado, North Carolina, Vermont, Texas, Oregon, Arkansas, Oklahoma, Kansas, Nebraska, Nevada, Arizona, Idaho, Montana, New Mexico, Tennessee, Alabama, Virginia, Kentucky, Utah, Washington, Wyoming, Georgia, Massachusetts, Ontario, and Québec. Any A- or B-graded lake in those states can appear in the top 25.