Lake Willoughby is a cold, clear oligotrophic lake in Orleans County, Vermont. Water quality is graded A based on 3 sampling years through 2025. Compared to the 29 other monitored lakes in Orleans County, Lake Willoughby ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Vermont DNR, last sampled 2025-08-13. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 28.2 ft down. Phosphorus level: 7.8 µg/L. Chlorophyll-a: 1.6 µg/L. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 28.2 ft | A |
| Phosphorus | 7.8 µg/L | A |
| Chlorophyll-a (Algae) | 1.6 µg/L | A |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lake Willoughby
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Fishing Lake Willoughby
Location
County Ranking
Ranked #5 of 30 lakes in Orleans County
Nearby Lakes in Orleans County
Explore Lake Willoughby across LakeGrade
More Vermont Lake Rankings
Other Grade A Lakes in Vermont
Oligotrophic Lakes in Vermont
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: 2025-08-13
Monitoring stations: 3