Safest Lakes to Swim in Vermont: Water Quality & Bacteria (2026)

Best-for-swimming on LakeQuality weights water clarity heavily: a swimmer cares whether they can see their feet, whether the water looks inviting on a 90-degree July day, and whether there is a real harmful-algal-bloom risk. The top Vermont swimming lake on current data is Lake St. Catherine (A).

The swimming-best list filters more aggressively on chlorophyll-a than the cleanest list — even very clear lakes can have harmful-algal-bloom risk under specific conditions, so the swimming ranking is more conservative on that front.

Rank	Lake	County	Advisories & grade	Clarity	Algae	Phosphorus	Area
1	Lake St. Catherine	Rutland	ALow algae	15.4 ft	2.7 µg/L	13.2 µg/L	1,024 acres
2	Malletts Bay Lake	Chittenden	ALow algae	13.8 ft	4 µg/L	10.2 µg/L	-
3	Peacham Pond	Caledonia	ALow algae	15.6 ft	2 µg/L	10.7 µg/L	331 acres
4	Wallingford Pond	Rutland	ALow algae	7.1 ft	3.9 µg/L	15.3 µg/L	-
5	Berlin Pond	Washington	ALow algae	21.7 ft	1.1 µg/L	7.1 µg/L	256 acres
6	Caspian Lake	Orleans	ALow algae	29.5 ft	1.3 µg/L	7.8 µg/L	789 acres
7	Harveys Lake	Caledonia	ALow algae	21 ft	1.3 µg/L	8.4 µg/L	409 acres
8	Maidstone Lake	Essex	ALow algae	28.5 ft	1.5 µg/L	7.2 µg/L	800 acres
9	Lake Groton	Caledonia	ALow algae	13.1 ft	3.3 µg/L	11.3 µg/L	414 acres
10	Rescue Lake	Windsor	ALow algae	15.1 ft	2.2 µg/L	10.7 µg/L	180 acres
11	Lake Hortonia	Rutland	ALow algae	14.8 ft	2.8 µg/L	15.5 µg/L	449 acres
12	Coles Pond	Caledonia	ALow algae	11.8 ft	2.9 µg/L	8.8 µg/L	125 acres
13	Seymour Lake	Orleans	ALow algae	24.6 ft	1.3 µg/L	7.8 µg/L	1,777 acres
14	Sabin Pond	Washington	ALow algae	15.7 ft	2.1 µg/L	9.7 µg/L	-
15	Lake Raponda	Windham	ALow algae	11.3 ft	2.4 µg/L	10.1 µg/L	-
16	Curtis Pond	Washington	ALow algae	15.3 ft	3.2 µg/L	13.2 µg/L	76 acres
17	Lowell Lake	Windham	ALow algae	13.5 ft	1.8 µg/L	8.2 µg/L	100 acres
18	Lake Fairlee	Orange	ALow algae	21.7 ft	2.7 µg/L	14.3 µg/L	463 acres
19	Echo Lake	Orleans	ALow algae	23 ft	1.6 µg/L	8 µg/L	508 acres
20	Echo Lake	Windsor	ALow algae	13.9 ft	1.6 µg/L	8.3 µg/L	76 acres
21	Echo Lake	Rutland	ALow algae	24.3 ft	1.3 µg/L	10.1 µg/L	-
22	Lake Morey	Orange	ALow algae	19.7 ft	2.8 µg/L	15.2 µg/L	-
23	Little Averill Pond	Essex	ALow algae	19.4 ft	1.6 µg/L	6.6 µg/L	483 acres
24	Lake Willoughby	Orleans	ALow algae	28.2 ft	1.6 µg/L	7.8 µg/L	-
25	South Pond	Lamoille	ALow algae	15.4 ft	2.3 µg/L	8.2 µg/L	109 acres

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All-states list →Minnesota version →Wisconsin version →Illinois version →Cleanest lakes in Vermont →Swimming safety guide →Algae bloom guide →

Frequently Asked Questions

What is the best lake to swim in Vermont?

Lake St. Catherine in Rutland County ranks #1 for swimming-safety in our 2026 Vermont dataset, combining grade-A water clarity with low algae and public access. The full top 25 above ranks the swim-safest lakes statewide.

How do you know if a lake is safe to swim in Vermont?

Three signals: (1) water clarity — Secchi depth above 6 feet is a strong sign of low suspended sediment and pathogens; (2) chlorophyll-a below 10 µg/L means low risk of harmful algae bloom; (3) a current grade of A or B from year-round sampling. VT DEC and county health departments post seasonal advisories — always check before you swim, especially in late summer when blue-green algae bloom risk peaks.

Are lakes in Vermont safe to swim in?

Most monitored Vermont lakes are safe to swim in under normal conditions, but water quality varies widely. The lakes ranked above are filtered to grade A and B with chlorophyll-a below 10 µg/L — meaning they consistently test cleaner and have lower algae bloom risk than the state average. Always check posted advisories before swimming and avoid water after heavy rain (bacterial contamination spikes from runoff).

What lakes have algae blooms in Vermont?

Algae blooms (especially blue-green / cyanobacteria) are most common in shallow, warm, nutrient-rich (eutrophic) lakes during late summer. Lakes with high phosphorus and chlorophyll-a measurements are at higher risk. The lakes on this page are filtered to exclude high-algae lakes. For the opposite list, see our most-polluted-lakes trend page.

When is it safe to swim in lakes in Vermont?

Vermont lakes are typically safest to swim in late spring through early summer (May–July), when water is cool and algae bloom risk is lowest. Risk rises in late summer and early fall (August–September) when warm water and accumulated nutrients drive cyanobacteria blooms. Always avoid swimming after heavy rainfall (bacterial spikes from runoff) and check current state DNR advisories the day you go.

What's the cleanest lake in Vermont?

The single cleanest lake by combined water-quality score leads our Vermont cleanest-lakes ranking, linked below. The lakes on this page are filtered specifically for swimming safety — same A/B grade requirement, plus low chlorophyll-a (active algae filter).

Our swimming-safety filter

We don't just rank by overall grade. Lakes here have to pass three filters:

Grade A or B overall water quality (top 40% statewide)
Chlorophyll-a below 10 µg/L — actively low algae density, low risk of harmful blue-green blooms
Multi-year sampling data — excludes lakes with limited sampling history (data confidence)

The Advisories & grade column adds a direct bacteria signal on top of the grade: where the EPA Water Quality Portal has enough E. coli or fecal-coliform samples, we show a historical swim-safety grade (how often the lake has exceeded the safe-swimming threshold). It is a record of past testing, never a live "safe today" reading — bacteria spike fast after rain. Where a lake carries an EPA 303(d) bacteria or recreation listing, that advisory runs above its letter in the table rather than beside it.

The ranking within the filter is by combined water-quality score (Secchi clarity + phosphorus + chlorophyll-a). Always check current VT DEC advisories before swimming.

Where to stay near Vermont swimming lakes

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Top-rated places to stay near Vermont swim lakes

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More on swimming water quality

Best Lakes for Swimming in America, Ranked (2026)

The highest-graded lakes for swimming, ranked on EPA nutrient and algae data — plus the one thing a letter grade cannot tell you the day you go.

Is It Safe to Swim in a Lake? E. coli and Advisories

What a swim advisory actually means, how E. coli monitoring works, how fast a lake clears after rain, and when a long-term grade is not a swim guide.

Lake Water Temperature by Month: How Warm Lakes Get

Typical lake surface temperatures month by month and state by state, from years of monitoring readings — when lakes warm up, how warm they get, and when they turn.

Best Month to Swim, by State — Typical Lake Temperatures

The month when well-graded lakes in each state are typically warmest, from long-run Water Quality Portal readings rather than this year’s weather.

Source: EPA National Aquatic Resource Surveys, 2026.