Lake · Penobscot County · ME
Is South Twin Lake safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 22, 2026 · EPA CyAN satellite
No bacteria advisory or sampling for this water.
Cyanobacteria No cyanobacteria bloom detected by satellite (below detection limit), imaged 2026-07-21.
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South Twin Lake is clear today. Be the first to know when it's not.
SwimZone checks this water every day and pings you the moment a bacteria or algae advisory goes up.
What's in the water at South Twin Lake right now
As of July 22, 2026, South Twin Lake in Penobscot County, Maine is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 21, 2026. Rainfall over the past week totaled 0.3 in, which can wash bacteria and nutrients into the water.
Blue-green algae at South Twin Lake
South Twin Lake is a lake in Penobscot County, Maine covering about 4.7 sq mi, the 50th-largest of the 319 lakes SwimZone monitors in Maine. Satellite imagery detected no blue-green algae bloom as of July 21, 2026.
Blue-green algae (cyanobacteria) blooms are most common from midsummer into early fall, when the water is warm, calm, and rich in nutrients from runoff. They can produce toxins that make people sick and can be rapidly fatal to dogs, so skip water that looks green, scummy, or like spilled paint, and keep children and pets out of it.
Bloom history at South Twin Lake
From EPA CyAN's satellite archive
Each bar is that summer's peak satellite reading (log scale). The red cap is the part above the advisory level.
Over 7 summers of satellite monitoring since 2020, South Twin Lake has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
When to swim at South Twin Lake
It is currently peak season for blue-green algae, when warm, calm water lets blooms form fastest. This water has no recorded advisory-level bloom in its satellite history, which makes it a comparatively steady summer swim spot; conditions still change between samples, so check the current read before you go.
Frequently asked: swimming in South Twin Lake
- Is it safe to swim in South Twin Lake right now?
- South Twin Lake is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 21, 2026. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
- Does South Twin Lake have blue-green algae (cyanobacteria)?
- No blue-green algae bloom is detectable at South Twin Lake as of July 21, 2026 (below the satellite's roughly 10,000 cells/mL detection limit). Cyanobacteria can still appear within hours in warm, calm, nutrient-rich water, so look before you swim.
- Can dogs swim in South Twin Lake?
- No bloom is detected at South Twin Lake today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.
- How often does South Twin Lake have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, South Twin Lake has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
- How many Maine lakes and beaches are unsafe for swimming today?
- Today, 15 Maine waters are above a safe-contact threshold and 33 more warrant caution, out of 457 monitored waters SwimZone tracks in the state.
- How is South Twin Lake's water quality measured?
- SwimZone builds this read from EPA CyAN satellite imagery for blue-green algae, official beach and fecal-bacteria advisories where a program monitors South Twin Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.
Before you swim: the basics
Swim spots near South Twin Lake
All Maine →All 6 monitored waters nearest South Twin Lake are clear today.
| Water | Distance | Today | Algae read | Sampled |
|---|---|---|---|---|
| North Twin LakeLake · Penobscot County | 1.9 mi | Clear to swim | None detected | Jul 21 |
| Turkey Tail LakeLake · Penobscot County | 3.2 mi | Clear to swim | None detected | Jul 21 |
| Elbow LakeLake · Penobscot County | 3.6 mi | Clear to swim | None detected | Jul 21 |
| Middle Jo-Mary LakeLake · Penobscot County | 4.5 mi | Clear to swim | None detected | Jul 21 |
| Upper Jo-Mary LakeLake · Piscataquis County | 5.1 mi | Clear to swim | None detected | Jul 21 |
| Quakish LakeLake · Penobscot County | 5.4 mi | Clear to swim | None detected | Jul 19 |