Is Mayo safe to swim?

As of July 19, 2026, Mayo in Barnstable County, Massachusetts carries a swim caution. Blue-green algae are not currently monitored at this water. No fecal-bacteria advisory is posted (state beach program). Rainfall over the past week totaled 3.0 in, which can wash bacteria and nutrients into the water.

How this read is built

Mayo is a lake in Barnstable County, Massachusetts. Blue-green algae are not currently monitored at this water.

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.

Is it safe to swim in Mayo right now?

Mayo carries a swim caution today. Blue-green algae are not currently monitored at this water. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.

Does Mayo have blue-green algae (cyanobacteria)?

Blue-green algae are not currently monitored at Mayo. Watch for green, blue-green, or paint-like scum and avoid the water if you see it.

Can dogs swim in Mayo?

No bloom is detected at Mayo 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 many Massachusetts lakes and beaches have swim advisories today?

Today, 5 Massachusetts waters are under a swim advisory and 229 more warrant caution, out of 608 monitored waters SwimZone tracks in the state.

How is Mayo'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 Mayo, and a recent-rainfall overlay, all refreshed daily. It was last updated July 19, 2026.