Lake · Ashland County · OH
Is Charles Mill Lake safe to swim?
Blue-green algae is above the safe-contact threshold.
Updated July 22, 2026 · EPA CyAN satellite
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There's an advisory on Charles Mill Lake right now.
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What's in the water at Charles Mill Lake right now
As of July 22, 2026, Charles Mill Lake in Ashland County, Ohio is not recommended for swimming. Satellite imagery measured 1,103,832 cells/mL of blue-green algae on July 21, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.6 in, which can wash bacteria and nutrients into the water.
Blue-green algae at Charles Mill Lake
Charles Mill Lake is a lake in Ashland County, Ohio covering about 2 sq mi, the 18th-largest of the 41 lakes SwimZone monitors in Ohio. Satellite imagery measured 1,103,832 cells/mL of blue-green algae on July 21, 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.
Bloom history at Charles Mill Lake
From EPA CyAN's satellite archive
Over 7 summers of satellite monitoring since 2020, Charles Mill Lake has reached blue-green algae advisory levels in 4 of them, most recently in June 2026. Its highest recorded reading was 1,946,718 cells/mL in September 2024.
Frequently asked: swimming in Charles Mill Lake
- Is it safe to swim in Charles Mill Lake right now?
- Charles Mill Lake is not recommended for swimming today. Satellite imagery measured 1,103,832 cells/mL of blue-green algae on July 21, 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 Charles Mill Lake have blue-green algae (cyanobacteria)?
- Yes. Satellite monitoring measured 1,103,832 cells/mL of blue-green algae (cyanobacteria) at Charles Mill Lake on July 21, 2026, above the 100,000 cells/mL advisory level. Avoid swimming and keep children and pets out of the water.
- Can dogs swim in Charles Mill Lake?
- No. Blue-green algae at Charles Mill Lake is above the safe-contact threshold (1,103,832 cells/mL on July 21, 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 Charles Mill Lake have blue-green algae blooms?
- Over 7 summers of satellite monitoring since 2020, Charles Mill Lake has reached blue-green algae advisory levels in 4 of them, most recently in June 2026. Its highest recorded reading was 1,946,718 cells/mL in September 2024.
- How many Ohio lakes and beaches are unsafe for swimming today?
- Today, 33 Ohio waters are above a safe-contact threshold and 32 more warrant caution, out of 101 monitored waters SwimZone tracks in the state.
- How is Charles Mill 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 Charles Mill Lake, and a recent-rainfall overlay, all refreshed daily. It was last updated July 22, 2026.