Published April 7, 2026 · Updated annually
Best Lakes for Swimming Across 12 States (2026)
Out of 5,469 monitored lakes across the 12 states we cover, these 15 earn the highest water quality grades. Each is graded A or B based on EPA Water Quality Portal data measuring water clarity, phosphorus concentration, and algae levels, the three factors that matter most for safe swimming.
Top 15 Lakes for Swimming
| Rank | Lake | State | County | Grade | Clarity (ft) | Area |
|---|---|---|---|---|---|---|
| 1 | East Fox Lake | MN | Crow Wing | A | 16.4 | 241 acres |
| 2 | North Long Lake | MN | Crow Wing | A | 15.1 | 6,190 acres |
| 3 | Bad Medicine Lake | MN | Becker | A | 25 | 803 acres |
| 4 | Big Sugar Bush Lake | MN | Becker | A | 16.5 | 522 acres |
| 5 | Round Lake | MN | Cook | A | 16.5 | 154 acres |
| 6 | Round Lake | MN | Beltrami | A | 18 | 181 acres |
| 7 | Horseshoe Lake | MN | Cass | A | 21 | 260 acres |
| 8 | Long Lake | MN | Cass | A | 21.5 | 1,007 acres |
| 9 | Long Lake | MN | Clearwater | A | 20.5 | 159 acres |
| 10 | Long Lake | MN | Beltrami | A | 20 | 412 acres |
| 11 | Long Lake | MN | Becker | A | 19.3 | 415 acres |
| 12 | Long Lake | MN | Itasca | A | 16.7 | 155 acres |
| 13 | Dead Lake | MN | Hubbard | A | 16 | 131 acres |
| 14 | West Twin Lake | MN | Crow Wing | A | 20 | - |
| 15 | Sunshine Lake | MN | St. Louis | A | 20 | 79 acres |
What Makes a Lake Safe for Swimming?
Water quality grades reflect three core measurements that directly impact swimming safety:
- Secchi depth (water clarity), How far you can see into the water. The top-graded lakes have clarity exceeding 15 feet, meaning you can see the bottom in many areas. High clarity means low algae and low suspended sediment.
- Phosphorus levels, The nutrient that feeds algae growth. Lakes graded A have phosphorus below 20 micrograms per liter. Higher phosphorus means more algae blooms, including potentially toxic cyanobacteria (blue-green algae).
- Chlorophyll-a, A direct measure of algae concentration. Top-rated swimming lakes have chlorophyll-a below 5 micrograms per liter, indicating minimal algae presence.
Why These Lakes Stand Out
The lakes on this list share common characteristics: they tend to be deeper (reducing warm-water algae growth), have forested or protected watersheds (less nutrient runoff), and benefit from geological features like sandy or rocky bottoms that limit phosphorus release from sediments.
These states are home to thousands of lakes, but water quality varies dramatically. A lake graded A may have crystal-clear water with 20+ feet of visibility, while an F-graded lake a few miles away could have visibility under 3 feet with frequent algae blooms.
Swimming Safety Tips
- Check the lake's current grade on LakeQuality before heading out
- Avoid swimming after heavy rain, runoff temporarily increases bacteria and nutrient levels
- If you see green scum or discolored water, stay out, it may indicate a harmful algae bloom
- Deeper water away from shore is generally cleaner than shallow nearshore areas
- Check your state's beach monitoring program for real-time advisories, Minnesota's program is one example, and every state health department runs a similar one
Frequently Asked Questions
Based on EPA monitoring data, the highest-graded lakes in Minnesota earn an A for water clarity, low phosphorus, and minimal algae. See the full table above for the current top 15, which spans all 12 states LakeQuality covers.
Most Wisconsin lakes are safe for swimming. Lakes graded A or B have excellent water quality. Lakes graded C are generally safe but may have moderate algae during warm months. Avoid swimming in lakes graded D or F, which may have harmful algae blooms.
Lake water quality is measured using three key indicators: secchi depth (water clarity), total phosphorus (nutrient levels), and chlorophyll-a (algae concentration). These measurements come from the EPA Water Quality Portal and state monitoring programs.
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