Updated August 2026

Where to Swim: Low-Algae Lakes Near You

Pick a lake for the weekend, then check the advisory before you get in. Every lake below cleared a low-algae filter on measured chlorophyll-a, and where the EPA has enough E. coli samples that record sits on the row. A letter grade scores nutrients and algae, not swimming, and bacteria spike fast after rain, so check your state or county health department the day you go. Use your location for the closest lakes, or browse the top 50 across US lakes with an A–F letter below.

Nutrient and algae grade A–B
Chlorophyll-a below 10 µg/L
Not a swim clearance

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Rank	Lake	County	State	Advisories & grade	Clarity	Algae	Area
1	Rainy Lake	Cass	MN	ALow algae	13.9 ft	1.8 µg/L	129 acres
2	Crane Lake	Otter Tail	MN	ALow algae	9 ft	6.4 µg/L	350 acres
3	Lobster Lake	Douglas	MN	ALow algae	13 ft	3.6 µg/L	1,334 acres
4	East Fox Lake	Crow Wing	MN	ALow algae	16.4 ft	2.7 µg/L	241 acres
5	Deep Portage Lake	Cass	MN	ALow algae	15.4 ft	1.6 µg/L	129 acres
6	Clearwater Lake	Cook	MN	ALow algae	29 ft	1.3 µg/L	462 acres
7	Clearwater Lake	Wright	MN	ALow algae	9.8 ft	6.3 µg/L	3,187 acres
8	Clearwater Lake	Clearwater	MN	ALow algae	10 ft	3.2 µg/L	999 acres
9	Lower Hay Lake	Crow Wing	MN	ALow algae	18.5 ft	2.7 µg/L	700 acres
10	Latoka Lake	Douglas	MN	ALow algae	19 ft	2.2 µg/L	767 acres
11	Big Cedar Lake-North Site-Near West Bend	Washington	WI	ALow algae	11.8 ft	3.6 µg/L	937 acres
12	Green Lake	Green Lake	WI	ALow algae	13.5 ft	4.4 µg/L	7,920 acres
13	Lake Beulah	Walworth	WI	ALow algae	10 ft	2.5 µg/L	812 acres
14	Geneva Lake	Walworth	WI	ABacteria B	21 ft	2.1 µg/L	5,401 acres
15	Powers Lake	Kenosha	WI	ALow algae	10 ft	3.4 µg/L	451 acres
16	Lac Courte Oreilles Lake	Sawyer	WI	ALow algae	12.2 ft	1.7 µg/L	5,139 acres
17	Whitefish Lake	Sawyer	WI	ALow algae	13.5 ft	1.6 µg/L	800 acres
18	Round Lake	Sawyer	WI	ALow algae	21.1 ft	0.9 µg/L	3,294 acres
19	Indian Lake	Sawyer	WI	ALow algae	6.5 ft	3.6 µg/L	76 acres
20	Big Lake	Shawano	WI	ALow algae	8 ft	2.7 µg/L	-
21	Lake Calumet	Cook	IL	ALow algae	4.1 ft	5.4 µg/L	0 acres
22	Crystal Lake	Montcalm	MI	ALow algae	10 ft	2.2 µg/L	709 acres
23	Ore Lake	Livingston	MI	ALow algae	9 ft	2.8 µg/L	229 acres
24	South Bar Lake	Leelanau	MI	ALow algae	8.5 ft	3.8 µg/L	78 acres
25	Eagle Lake	Kalkaska	MI	ALow algae	18 ft	1.3 µg/L	25 acres
26	Ellen Lake	Iron	MI	ALow algae	17.3 ft	1.8 µg/L	140 acres
27	Brooks Lake	Leelanau	MI	ALow algae	9.5 ft	3.2 µg/L	7 acres
28	Indian Lake	Kalamazoo	MI	ALow algae	9.5 ft	2.8 µg/L	790 acres
29	Round Lake	Mecosta	MI	ALow algae	9 ft	6.8 µg/L	157 acres
30	Mecosta Lake	Mecosta	MI	ALow algae	9.5 ft	3.3 µg/L	312 acres
31	Perch Lake	Iron	MI	ALow algae	6 ft	4.8 µg/L	1,046 acres
32	West Okoboji Lake	Dickinson	IA	Bacteria A · advisoryAnutrients and algae	15.7 ft	2.3 µg/L	-
33	Dale Maffitt Reservoir	Dallas	IA	ALow algae	9.8 ft	2.1 µg/L	230 acres
34	Blue Pit Lake	Cerro Gordo	IA	ALow algae	17.1 ft	2.4 µg/L	-
35	Ada Hayden Heritage Park Lake	Story	IA	ALow algae	6.8 ft	5.2 µg/L	-
36	Little Sioux Park Lake	Woodbury	IA	ABacteria A	5.7 ft	5.7 µg/L	-
37	Rudd Lake	Floyd	IA	ALow algae	8.1 ft	4.5 µg/L	-
38	Slipbluff Lake	Decatur	IA	ALow algae	9 ft	4.5 µg/L	18 acres
39	Lacey Keosauqua Lake	Van Buren	IA	ALow algae	7.1 ft	4.7 µg/L	23 acres
40	Yenruogis Pond	Keokuk	IA	ALow algae	9.9 ft	6.2 µg/L	-
41	Sand Lake	Marshall	IA	ALow algae	6.4 ft	3.6 µg/L	-
42	Queneska Island Lake	Essex	NY	ALow algae	17.4 ft	3.4 µg/L	-
43	South Lake	Herkimer	NY	ALow algae	—	1.1 µg/L	499 acres
44	West Pond	Herkimer	NY	ALow algae	—	3.3 µg/L	-
45	Squash Pond	Herkimer	NY	ALow algae	—	2 µg/L	-
46	Sherwood Lake	Warren	MO	ALow algae	5.9 ft	4.4 µg/L	145 acres
47	Lake Taneycomo @ Rockaway Beach	Taney	MO	ALow algae	8.7 ft	1.1 µg/L	-
48	Fox Valley Lake	Clark	MO	ALow algae	8.5 ft	3.6 µg/L	96 acres
49	Bull Shoals Lake	Taney	MO	ALow algae	8.1 ft	4 µg/L	-
50	Lake Shayne-Terre du Lac Lakes	Washington	MO	ALow algae	11.1 ft	1.2 µg/L	51 acres

A bacteria grade summarises past E. coli or fecal-coliform sampling, never today's water. Where a lake carries an EPA 303(d) bacteria or recreation listing, that advisory runs above its letter in the table.

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Frequently Asked Questions

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

Start with the posted advisory. State environmental agencies and county health departments close beaches for harmful algal blooms and bacteria spikes, and that same-day notice is the only source that reflects today's water. Three measurements help you shortlist before you drive: E. coli or fecal-coliform sampling where the EPA Water Quality Portal has enough of it, chlorophyll-a (low values mean low algae density), and Secchi clarity depth. Every lake below cleared a grade of A or B on nutrients and algae plus a chlorophyll-a reading under 10 µg/L. That filter describes the water's measured condition. It is not a clearance to swim.

What is the 80/20 rule in swimming?

The 80/20 rule is a swim-training concept (80% easy aerobic work, 20% high intensity), unrelated to water quality. For lake-swimming safety, the relevant rule is the EPA recreational water guideline: total bacteria below 235 colonies per 100 mL for primary contact recreation.

What lakes are you not allowed to swim in?

Most US lakes allow swimming, but individual lakes close seasonally for harmful algal blooms (HABs), elevated bacteria, or storm runoff, and state environmental agencies and county health departments post those closures. Some reservoirs prohibit swimming year-round, usually drinking-water sources, hazardous bottom conditions, or restricted access. Public access is not one of the filters on this page: each lake page carries whatever access record exists for that lake, and for many lakes there is none. Confirm access with the agency that manages the water before you drive out.

What are the risks of swimming in a lake?

The main risks are: (1) blue-green algae blooms (cyanobacteria) which produce toxins that cause skin irritation, gastrointestinal illness, or worse if swallowed; (2) bacterial contamination after heavy rain (E. coli from agricultural or sewage runoff); (3) underwater hazards like submerged rocks, weeds, or sudden depth changes. Swimmer safety: never swim alone, check advisories, avoid swimming after heavy rain, and stay out of visibly green or scummy water.

Can you get sick from swimming in a lake?

Yes, though it is uncommon in well-monitored water. The usual illnesses are gastrointestinal (from swallowing water carrying E. coli or other bacteria), skin rashes (from blue-green algae toxins), and ear infections. Check the posted advisory first, stay out of the water for a day or two after heavy rain, avoid visibly green or scummy water, keep it out of your mouth, and rinse off afterward. The lakes ranked above are filtered on measured nutrients and algae, which is a different measurement from a bacteria reading.