Lake: Summit Lake is a cold, clear oligotrophic lake in Thurston County, Washington. Water quality is graded A based on 2 sampling years through 2025. Compared to the 18 other monitored lakes in Thurston County, Lake: Summit Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Washington DNR, last sampled 2025-12-04. Grade methodology: LakeGrade methodology.
Watch Lake: Summit Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
No clarity data. Phosphorus level: 6 µg/L. Chlorophyll-a: 1.3 µg/L. Trophic State Index: 32.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 6 µg/L | A |
| Chlorophyll-a (Algae) | 1.3 µg/L | A |
| Trophic State Index (TSI) | 32 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lake: Summit Lake
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Fishing Lake: Summit Lake
Location
County Ranking
Ranked #3 of 19 lakes in Thurston County
Nearby Lakes in Thurston County
Explore Lake: Summit Lake across LakeGrade
More Washington Lake Rankings
Other Grade A Lakes in Washington
Oligotrophic Lakes in Washington
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-12-04
Monitoring stations: 1