Beach · Cook County · IL
Is Marion Mahoney Griffin Beach safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 19, 2026 · Illinois beach program (EPA BEACON)
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What's in the water at Marion Mahoney Griffin Beach right now
As of July 19, 2026, Marion Mahoney Griffin Beach in Cook County, Illinois 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 0.0 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Marion Mahoney Griffin Beach
Marion Mahoney Griffin Beach is a lake in Cook County, Illinois. 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 Marion Mahoney Griffin Beach
- Is it safe to swim in Marion Mahoney Griffin Beach right now?
- Marion Mahoney Griffin Beach 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 Marion Mahoney Griffin Beach have blue-green algae (cyanobacteria)?
- Blue-green algae are not currently monitored at Marion Mahoney Griffin Beach. Watch for green, blue-green, or paint-like scum and avoid the water if you see it.
- Can dogs swim in Marion Mahoney Griffin Beach?
- No bloom is detected at Marion Mahoney Griffin Beach 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 Illinois lakes and beaches have swim advisories today?
- Today, 53 Illinois waters are under a swim advisory and 7 more warrant caution, out of 138 monitored waters SwimZone tracks in the state.
- How is Marion Mahoney Griffin Beach'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 Marion Mahoney Griffin Beach, and a recent-rainfall overlay, all refreshed daily. It was last updated July 19, 2026.