Is Thunder Lake Safe for Swimming?
Thunder Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Excellent for swimming, crystal clear water with minimal algae. Water clarity: 16.4 ft visibility. Phosphorus: 10 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | A (Excellent) |
| Water Clarity (Secchi Depth) | 16.4 ft |
| Phosphorus | 10 μg/L |
| Location | Cass County, Minnesota |
How does Thunder Lake compare?
With an overall water quality grade of A, Thunder Lake matches or beats the Minnesota state average of Grade C. It ranks #17 of 132 lakes in Cass County by water quality score.
Water clarity (Secchi depth) sits at 16.4 feet. That counts as exceptional clarity — sunlight penetrates deep, supporting submerged plants and limiting algae.