Seeley Lake
Missoula County, MontanaView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↓ down from A at the last regrade
- Oligotrophic
- #8 of 40 in the county
- Limited data
Seeley Lake in Missoula County, Montana has a water quality grade of B (Good). Water clarity: 15.4 ft visibility. Phosphorus: 8.9 µg/L.
- Clarity
- 15.4 ft
- Type
- Oligotrophic
- Phosphorus
- 8.9 µg/L
- Trend
- → Stable
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Watch Seeley Lake’s letter
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Seeley Lake is a cold, clear oligotrophic lake in Missoula County, Montana. Water quality is graded B based on 2 sampling years through 2022. Phosphorus level is declining over recent sampling years. Compared to the 39 other monitored lakes in Missoula County, Seeley Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Montana DEQ, last sampled 2022-09-20. Grade methodology: LakeQuality methodology.
What Seeley Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.4 ft of visibility
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
Crystal clear, you can see 15.4 ft down. Phosphorus 8.9 µg/L. TSI 37. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.4 ft | Not graded |
| Phosphorus | 8.9 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Fishing Seeley Lake
Water Quality Trend: → Stable
Based on 13 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.072 m/yr | 8 |
| Phosphorus | ↓ Declining | +0.23 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -1.4 µg/L/yr | 2 |
County Ranking
Ranked #8 of 40 lakes in Missoula County
Nearby Lakes in Missoula County
Frequently asked questions about Seeley Lake
Where is Seeley Lake?
- Seeley Lake is a lake in Missoula County, Montana. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Seeley Lake?
- Seeley Lake in Missoula County, Montana has a water quality grade of B (Good). Water clarity: 15.4 ft visibility. Phosphorus: 8.9 µg/L.
Is Seeley Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Seeley Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Montana's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
Montana's cleanest and most-polluted lakes, ranked
More Montana Lake Rankings
Other Grade B Lakes in Montana
Oligotrophic Lakes in Montana
Where this data comes from
79 measurements from 1 monitoring station, 2012–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Montana Volunteer Water Quality Monitoring
MTVOLWQM_WQX79 samples · 2012–2022
Analytical methods
- Phosphorus by Colorimetry
- 4500 N C ~ Persufate Method for Total Nitrogen
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.