Is Stink Lake safe to swim?

As of July 20, 2026, Stink Lake in Codington County, South Dakota carries a swim caution. Satellite imagery measured 56,144 cells/mL of blue-green algae on July 19, 2026, elevated but below 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

Stink Lake is a lake in Codington County, South Dakota covering about 0.5 sq mi, the 101st-largest of the 127 lakes SwimZone monitors in South Dakota. Satellite imagery measured 56,144 cells/mL of blue-green algae on July 19, 2026, elevated but below 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, Stink 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 1,465,895 cells/mL in July 2023.

Is it safe to swim in Stink Lake right now?

Stink Lake carries a swim caution today. Satellite imagery measured 56,144 cells/mL of blue-green algae on July 19, 2026, elevated but below 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 Stink Lake have blue-green algae (cyanobacteria)?

Low levels. Satellite monitoring measured 56,144 cells/mL at Stink Lake on July 19, 2026, below the 100,000 cells/mL advisory threshold. Keep an eye out for surface scum, which can concentrate quickly.

Can dogs swim in Stink Lake?

Use caution. Blue-green algae at Stink Lake are elevated (56,144 cells/mL on July 19, 2026). Dogs are far more sensitive to cyanobacteria than people, so keep them out of the water and away from surface scum.

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

Over 7 summers of satellite monitoring since 2020, Stink 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 1,465,895 cells/mL in July 2023.

How many South Dakota lakes and beaches are unsafe for swimming today?

Today, 89 South Dakota waters are above a safe-contact threshold and 3 more warrant caution, out of 142 monitored waters SwimZone tracks in the state.

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