Lost Coon Lake
Flathead County, MontanaView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Limited data
Lost Coon Lake in Flathead County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.8 ft visibility.
- Clarity
- 11.8 ft
- Trend
- ↓ Declining
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Stays near Lost Coon Lake
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Top-rated places to stay near Lost Coon Lake
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Watch Lost Coon Lake’s letter
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Why Lost Coon Lake has no grade
Lost Coon Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Lost Coon Lake is Not Rated — not an F. Its 11.8-foot median from 21 readings collected 2020–2023 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Montana DEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lost Coon Lake is a lake in Flathead County, Montana. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2023-10-07. Grade methodology: LakeQuality methodology.
What Lost Coon Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.8 ft of visibility
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Lost Coon Lake
These readings exist but are not enough for an A–F grade — see why.
Good clarity, visible to about 11.8 ft. TSI 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.8 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Fishing Lost Coon Lake
Water Quality Trend: ↓ Declining
Based on 12 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.054 m/yr | 3 |
| Phosphorus | ↓ Declining | +0.32 µg/L/yr | 11 |
| Chlorophyll-a | ↓ Declining | +0.04 µg/L/yr | 12 |
Graded lakes near Lost Coon Lake
Lost Coon Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Flathead County
Frequently asked questions about Lost Coon Lake
Where is Lost Coon Lake?
- Lost Coon Lake is a lake in Flathead County, Montana. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Lost Coon Lake?
- Lost Coon Lake in Flathead County, Montana is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.8 ft visibility.
Is Lost Coon Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Explore Lost Coon Lake across LakeQuality
Planning a trip around Glacier?
Lost Coon Lake is about 32 miles from Glacier National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Glacier →More Montana Lake Rankings
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Where this data comes from
21 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS21 samples · 2020–2023
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.