Lake · Delaware County · OK
Is Grand Lake O' the Cherokees safe to swim?
No advisory or algae bloom reported for this water today.
Updated July 20, 2026 · EPA CyAN satellite
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What's in the water at Grand Lake O' the Cherokees right now
As of July 20, 2026, Grand Lake O' the Cherokees in Delaware County, Oklahoma is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Grand Lake O' the Cherokees
Grand Lake O' the Cherokees is a lake in Delaware County, Oklahoma covering about 60 sq mi, the 1st-largest of the 57 lakes SwimZone monitors in Oklahoma. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Larger, warmer waters like this can hold a bloom for weeks once nutrients and calm weather line up.
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 Grand Lake O' the Cherokees
From EPA CyAN's satellite archive
Over 7 summers of satellite monitoring since 2020, Grand Lake O' the Cherokees 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 Grand Lake O' the Cherokees
- Is it safe to swim in Grand Lake O' the Cherokees right now?
- Grand Lake O' the Cherokees is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 19, 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 Grand Lake O' the Cherokees have blue-green algae (cyanobacteria)?
- No blue-green algae bloom is detectable at Grand Lake O' the Cherokees as of July 19, 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 Grand Lake O' the Cherokees?
- No bloom is detected at Grand Lake O' the Cherokees 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 Grand Lake O' the Cherokees have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, Grand Lake O' the Cherokees has not reached a blue-green algae advisory level. Conditions can still change quickly, so check the current read before you swim.
- How many Oklahoma lakes and beaches are unsafe for swimming today?
- Today, 22 Oklahoma waters are above a safe-contact threshold and 2 more warrant caution, out of 64 monitored waters SwimZone tracks in the state.
- How is Grand Lake O' the Cherokees'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 Grand Lake O' the Cherokees, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.