Safest Lakes to Swim In in Illinois
17 lakes in Illinois qualify as safest for swimming, all hold grade A or B and report chlorophyll-a (algae) under 10 µg/L. Always check local advisories on the day you swim.
Ranked List
| # | Lake | County | Grade | Clarity | Phosphorus | Algae |
|---|---|---|---|---|---|---|
| 1 | Axehead Lake | Cook | A | 11.9 ft | 10 µg/L | - |
| 2 | Powderhorn Lake | Cook | A | 10.1 ft | 13 µg/L | - |
| 3 | Baumann Park Lake | Winnebago | A | 10.2 ft | 11.5 µg/L | - |
| 4 | Silver Lake | McHenry | B | 7 ft | 11 µg/L | - |
| 5 | Boulder South Lake | Perry | B | 8.8 ft | 14.5 µg/L | - |
| 6 | Wampum Lake | Cook | B | 6.9 ft | 16 µg/L | - |
| 7 | Round Lake | Lake | B | 7.4 ft | 19.5 µg/L | - |
| 8 | Big Rock Lake | Kane | B | 8.1 ft | 10 µg/L | - |
| 9 | Flatfoot Lake | Cook | B | 6.3 ft | 10.5 µg/L | - |
| 10 | Opeka Lake | Cook | B | 3.9 ft | 15.5 µg/L | - |
| 11 | One Horse Gap Lake | Pope | B | 4 ft | 17 µg/L | - |
| 12 | Glendale Lake | Pope | B | 4.8 ft | 16 µg/L | - |
| 13 | Tecumseh Lake | Hardin | B | 3.6 ft | 18 µg/L | - |
| 14 | Grays Lake | Lake | B | 3.5 ft | 18 µg/L | - |
| 15 | Calumet Lake | Cook | B | 4.3 ft | 10.5 µg/L | - |
| 16 | Lily Lake | McHenry | B | 3.3 ft | 16 µg/L | - |
| 17 | Catherine Lake | Lake | B | 7.4 ft | 27.5 µg/L | - |