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

Swimming-friendly is a clarity-plus-algae problem: clear water and a low chlorophyll-a number. Smiw Lake (A) tops the Alabama list on those combined measures.

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	Smiw Lake	Winston	ALow algae	11.5 ft	2.7 µg/L	8 µg/L	-
2	Lake Andrews	Houston	ALow algae	5.9 ft	6.2 µg/L	25 µg/L	1,540 acres
3	Tust Lake	Tuscaloosa	ALow algae	7.7 ft	5.3 µg/L	12 µg/L	-
4	Inlb Lake	Blount	ALow algae	11.9 ft	2.8 µg/L	12 µg/L	-
5	Thue Lake	Elmore	ALow algae	5.8 ft	2.7 µg/L	9 µg/L	574 acres
6	Clam Lake	Wilcox	ALow algae	3 ft	6.1 µg/L	26 µg/L	-
7	Clam Lake	Monroe	ALow algae	3 ft	6.1 µg/L	32.5 µg/L	5,850 acres
8	Mare Lake	Elmore	ALow algae	10.6 ft	4.5 µg/L	8 µg/L	-
9	Mare Lake	Randolph	ALow algae	11.5 ft	5.3 µg/L	12 µg/L	10,661 acres
10	Yate Lake	Tallapoosa	ALow algae	4.7 ft	3.2 µg/L	9 µg/L	2,000 acres
11	Yate Lake	Tallapoosa	ALow algae	7.4 ft	1.1 µg/L	7 µg/L	40,000 acres
12	Bclm Lake	Mobile	ALow algae	6.9 ft	1.2 µg/L	28 µg/L	-
13	Shlb Lake	Baldwin	ALow algae	4.4 ft	1.1 µg/L	32.5 µg/L	-
14	Olit Lake	Tuscaloosa	BLow algae	4.3 ft	7.5 µg/L	19 µg/L	-
15	Ptac Lake	Covington	BLow algae	3.6 ft	7.5 µg/L	18 µg/L	700 acres
16	Fjac Lake	Covington	BLow algae	3.9 ft	8.5 µg/L	14 µg/L	-
17	Danw Lake	Dallas	BLow algae	3.1 ft	7.1 µg/L	31 µg/L	-
18	Danw Lake	Wilcox	BLow algae	2.9 ft	7.5 µg/L	23 µg/L	17,200 acres
19	Danw Lake	Wilcox	BLow algae	2.9 ft	8.7 µg/L	27 µg/L	-
20	Danw Lake	Dallas	BLow algae	3 ft	8.9 µg/L	30 µg/L	-
21	Wdfa Lake	Montgomery	BLow algae	3.7 ft	8 µg/L	24 µg/L	-
22	Wdfa Lake	Lowndes	BLow algae	3.3 ft	9.1 µg/L	34 µg/L	12,300 acres

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

Frequently Asked Questions

What is the best lake to swim in Alabama?

Smiw Lake in Winston County ranks #1 for swimming-safety in our 2026 Alabama 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 Alabama?

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. ADEM 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 Alabama safe to swim in?

Most monitored Alabama 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 Alabama?

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 Alabama?

Alabama 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 Alabama?

The single cleanest lake by combined water-quality score leads our Alabama 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 ADEM advisories before swimming.

Where to stay near Alabama swimming lakes

Book a cabin, resort, or rental near Alabama's cleanest swim lakes — live availability and prices for your beach weekend.

Top-rated places to stay near Alabama 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.