Is Dewey Lake safe to swim?

As of July 20, 2026, Dewey Lake in Floyd County, Kentucky is not recommended for swimming. Satellite imagery measured 3,633,649 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.2 in, which can wash bacteria and nutrients into the water.

How this read is built

Dewey Lake is a lake in Floyd County, Kentucky covering about 1.7 sq mi, the 8th-largest of the 11 lakes SwimZone monitors in Kentucky. Satellite imagery measured 3,633,649 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold.

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.

Over 7 summers of satellite monitoring since 2020, Dewey Lake has reached blue-green algae advisory levels in 7 of them, most recently in July 2026. This is a lake that blooms most summers. Its highest recorded reading was 5,254,156 cells/mL in August 2023.

Is it safe to swim in Dewey Lake right now?

Dewey Lake is not recommended for swimming today. Satellite imagery measured 3,633,649 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.

Does Dewey Lake have blue-green algae (cyanobacteria)?

Yes. Satellite monitoring measured 3,633,649 cells/mL of blue-green algae (cyanobacteria) at Dewey Lake on July 19, 2026, above the 100,000 cells/mL advisory level. Avoid swimming and keep children and pets out of the water.

Can dogs swim in Dewey Lake?

No. Blue-green algae at Dewey Lake is above the safe-contact threshold (3,633,649 cells/mL on July 19, 2026). Cyanobacteria toxins can be rapidly fatal to dogs, which swallow it while swimming and lick it from their fur. Keep dogs out of the water and away from any scum along the shore.

How often does Dewey Lake have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Dewey Lake has reached blue-green algae advisory levels in 7 of them, most recently in July 2026. This is a lake that blooms most summers. Its highest recorded reading was 5,254,156 cells/mL in August 2023.

How many Kentucky lakes and beaches are unsafe for swimming today?

Today, 3 Kentucky waters are above a safe-contact threshold and 0 more warrant caution, out of 12 monitored waters SwimZone tracks in the state.

How is Dewey 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 Dewey Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 20, 2026.