Is Lake Conroe safe to swim?

As of July 20, 2026, Lake Conroe in Montgomery County, Texas is not recommended for swimming. Satellite imagery measured 225,415 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 12.5 in, which can wash bacteria and nutrients into the water.

How this read is built

Lake Conroe is a lake in Montgomery County, Texas covering about 30.9 sq mi, the 16th-largest of the 218 lakes SwimZone monitors in Texas. Satellite imagery measured 225,415 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 Conroe 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 498,819 cells/mL in July 2025.

Is it safe to swim in Lake Conroe right now?

Lake Conroe is not recommended for swimming today. Satellite imagery measured 225,415 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 Conroe have blue-green algae (cyanobacteria)?

Yes. Satellite monitoring measured 225,415 cells/mL of blue-green algae (cyanobacteria) at Lake Conroe 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 Conroe?

No. Blue-green algae at Lake Conroe is above the safe-contact threshold (225,415 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 Conroe have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Lake Conroe 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 498,819 cells/mL in July 2025.

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

Today, 78 Texas waters are above a safe-contact threshold and 85 more warrant caution, out of 399 monitored waters SwimZone tracks in the state.

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