Is Lake Sarah safe to swim?

As of July 20, 2026, Lake Sarah in Hennepin County, Minnesota is not recommended for swimming. Satellite imagery measured 2,307,932 cells/mL of blue-green algae on July 19, 2026, above the 100,000 cells/mL advisory threshold. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.

How this read is built

Lake Sarah is a lake in Hennepin County, Minnesota covering about 0.9 sq mi, the 490th-largest of the 960 lakes SwimZone monitors in Minnesota. Satellite imagery measured 2,307,932 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, Lake Sarah 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 2,374,340 cells/mL in July 2026.

Is it safe to swim in Lake Sarah right now?

Lake Sarah is not recommended for swimming today. Satellite imagery measured 2,307,932 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 Sarah have blue-green algae (cyanobacteria)?

Yes. Satellite monitoring measured 2,307,932 cells/mL of blue-green algae (cyanobacteria) at Lake Sarah 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 Sarah?

No. Blue-green algae at Lake Sarah is above the safe-contact threshold (2,307,932 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 Sarah have blue-green algae blooms?

Over 7 summers of satellite monitoring since 2020, Lake Sarah 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 2,374,340 cells/mL in July 2026.

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

Today, 307 Minnesota waters are above a safe-contact threshold and 34 more warrant caution, out of 1162 monitored waters SwimZone tracks in the state.

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