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LakeQuality

Pine Mountain Lake vs Thunder Lake

Water quality, depth, fish species, and recreation comparison.

Thunder Lake has a higher water quality grade (A, Excellent) than Pine Mountain Lake (A, Excellent). Both are in Cass County, Minnesota.

Pine Mountain Lake and Thunder Lake are both in Minnesota — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. The grades are close: Pine Mountain Lake (A) and Thunder Lake (A) are within one letter of each other on the LakeGrade rubric. The per-parameter sub-grades below will show where the small differences actually live.

With grades this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.

A

Pine Mountain Lake

Cass County, Minnesota

Good clarity, visible to about 12.5 ft.

A

Thunder Lake

Cass County, Minnesota

Crystal clear, you can see 16.4 ft down.

Side-by-Side Metrics

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

MetricPine Mountain LakeThunder Lake
Overall GradeA (Excellent)A (Excellent)
Water Clarity12.5 ft16.4 ft
Phosphorus17.5 µg/L10 µg/L
Chlorophyll-a (Algae)No dataNo data
Maximum Depth--
Surface Area1.6K acres1.3K acres
Public AccessUnknownUnknown
Fish Species11
Trophic Statemesotrophicoligotrophic

Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).

Verdict

Thunder Lake wins on overall water quality with a Grade A versus Pine Mountain Lake's Grade A. Water clarity: 16.4 ft vs 12.5 ft. For fishing diversity, Thunder Lake also leads with 1 species.