Is Lake Mattamuskeet safe to swim?

As of July 20, 2026, Lake Mattamuskeet in Hyde County, North Carolina is not recommended for swimming. Satellite imagery measured 1,689,285 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 3.4 in, which can wash bacteria and nutrients into the water.

How this read is built

Lake Mattamuskeet is a lake in Hyde County, North Carolina covering about 40.8 sq mi, the 3rd-largest of the 44 lakes SwimZone monitors in North Carolina. Satellite imagery measured 1,689,285 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. 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.

Over 7 summers of satellite monitoring since 2020, Lake Mattamuskeet 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 2,243,381 cells/mL in September 2024.

Is it safe to swim in Lake Mattamuskeet right now?

Lake Mattamuskeet is not recommended for swimming today. Satellite imagery measured 1,689,285 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 Lake Mattamuskeet have blue-green algae (cyanobacteria)?

Yes. Satellite monitoring measured 1,689,285 cells/mL of blue-green algae (cyanobacteria) at Lake Mattamuskeet 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 Lake Mattamuskeet?

No. Blue-green algae at Lake Mattamuskeet is above the safe-contact threshold (1,689,285 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 Lake Mattamuskeet have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Lake Mattamuskeet 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 2,243,381 cells/mL in September 2024.

How many North Carolina lakes and beaches are unsafe for swimming today?

Today, 13 North Carolina waters are above a safe-contact threshold and 96 more warrant caution, out of 255 monitored waters SwimZone tracks in the state.

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