Beach · Nantucket County · MA
Is 40th Pole safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 19, 2026 · Massachusetts beach program (EPA BEACON)
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What's in the water at 40th Pole right now
As of July 19, 2026, 40th Pole in Nantucket County, Massachusetts is clear to swim. 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 0.5 in, which can wash bacteria and nutrients into the water.
Blue-green algae at 40th Pole
40th Pole is a lake in Nantucket 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.
Frequently asked: swimming in 40th Pole
- Is it safe to swim in 40th Pole right now?
- 40th Pole is clear to swim 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 40th Pole have blue-green algae (cyanobacteria)?
- Blue-green algae are not currently monitored at 40th Pole. Watch for green, blue-green, or paint-like scum and avoid the water if you see it.
- Can dogs swim in 40th Pole?
- No bloom is detected at 40th Pole 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 40th Pole'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 40th Pole, and a recent-rainfall overlay, all refreshed daily. It was last updated July 19, 2026.