SwimZone

Lake · Piscataquis County · ME

Is Shallow Lake safe to swim?

Advisory

Blue-green algae is above the safe-contact threshold.

Updated July 22, 2026 · EPA CyAN satellite

Recent rain
0.1 in
Water type
Lake
Last updated
Jul 22
Bacteria
E. coli, fecal
Not monitored
Tested
Not monitored

No bacteria advisory or sampling for this water.

Blue-green algae
cyanobacteria
Advisory
Tested
307,966
cells/mL
Advisory over
100,000
cells/mL

Cyanobacteria 307,966 cells/mL (satellite, 7-day max), imaged 2026-07-21.

Sampled Jul 21 · EPA CyAN satellite

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There's an advisory on Shallow Lake right now.

Get an alert the day it clears, and every time a new one goes up.

What's in the water at Shallow Lake right now

As of July 22, 2026, Shallow Lake in Piscataquis County, Maine is not recommended for swimming. Satellite imagery measured 307,966 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.1 in, which can wash bacteria and nutrients into the water.

How this read is built

Blue-green algae at Shallow Lake

Shallow Lake is a lake in Piscataquis County, Maine covering about 1.7 sq mi, the 132nd-largest of the 319 lakes SwimZone monitors in Maine. Satellite imagery measured 307,966 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold.

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 Shallow Lake

From EPA CyAN's satellite archive

2020: peak 1,013,778 cells/mL — above the 100,000 advisory level202021: peak 855,112 cells/mL — above the 100,000 advisory level212022: peak 458,124 cells/mL — above the 100,000 advisory level222023: peak 365,109 cells/mL — above the 100,000 advisory level232024: peak 420,749 cells/mL — above the 100,000 advisory level242025: peak 558,757 cells/mL — above the 100,000 advisory level252026: peak 763,384 cells/mL — above the 100,000 advisory level26Advisory100k cells/mL

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, Shallow Lake has reached blue-green algae advisory levels in 7 of them, most recently in June 2026. This is a lake that blooms most summers. Its highest recorded reading was 1,013,778 cells/mL in September 2020.

When to swim at Shallow Lake

It is currently peak season for blue-green algae, when warm, calm water lets blooms form fastest. This lake has bloomed in most monitored summers (7 of 7), historically peaking around September. Early summer, before the water fully warms, has generally been the safer window here; check the current read before you go either way.

Frequently asked: swimming in Shallow Lake

Is it safe to swim in Shallow Lake right now?
Shallow Lake is not recommended for swimming today. Satellite imagery measured 307,966 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.
Does Shallow Lake have blue-green algae (cyanobacteria)?
Yes. Satellite monitoring measured 307,966 cells/mL of blue-green algae (cyanobacteria) at Shallow Lake on July 21, 2026, above the 100,000 cells/mL advisory level. Avoid swimming and keep children and pets out of the water.
Can dogs swim in Shallow Lake?
No. Blue-green algae at Shallow Lake is above the safe-contact threshold (307,966 cells/mL on July 21, 2026). Cyanobacteria toxins can be rapidly fatal to dogs, which swallow it while swimming and lick it from their fur. Keep dogs out of the water and away from any scum along the shore.
How often does Shallow Lake have blue-green algae blooms?
Over 7 summers of satellite monitoring since 2020, Shallow Lake has reached blue-green algae advisory levels in 7 of them, most recently in June 2026. This is a lake that blooms most summers. Its highest recorded reading was 1,013,778 cells/mL in September 2020.
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 Shallow 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 Shallow Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.

Before you swim: the basics

Swim spots near Shallow Lake

All Maine →

Of the 6 monitored waters nearest Shallow Lake, 1 is flagged today.

WaterDistanceTodayAlgae readSampled
Little Shallow LakeLake · Piscataquis County1.9 miClear to swimNone detectedJul 21
Daggett PondPond · Piscataquis County2.2 miClear to swimNone detectedJul 19
Round PondPond · Piscataquis County4.0 miClear to swimNone detectedJul 19
Longley PondPond · Piscataquis County4.9 miUse caution41,094 cells/mLJul 21
Rowe PondPond · Piscataquis County6.2 miClear to swimNone detectedJul 21
Umbazooksus LakeLake · Piscataquis County6.3 miClear to swimNone detectedJul 21