Lake · Franklin County · ME
Is Porter Lake safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 22, 2026 · EPA CyAN satellite
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Porter 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 Porter Lake right now
As of July 22, 2026, Porter Lake in Franklin 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 Porter Lake
Porter Lake is a lake in Franklin County, Maine covering about 0.8 sq mi, the 239th-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 Porter Lake
From EPA CyAN's satellite archive
Over 7 summers of satellite monitoring since 2020, Porter Lake has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
Frequently asked: swimming in Porter Lake
- Is it safe to swim in Porter Lake right now?
- Porter 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 Porter Lake have blue-green algae (cyanobacteria)?
- No blue-green algae bloom is detectable at Porter 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 Porter Lake?
- No bloom is detected at Porter 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 Porter Lake have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, Porter 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 Porter 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 Porter Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.