Is Hart Lake safe to swim?

As of July 20, 2026, Hart Lake in Itasca County, Minnesota is clear to swim. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Rainfall over the past week totaled 0.0 in, which can wash bacteria and nutrients into the water.

How this read is built

Hart Lake is a lake in Itasca County, Minnesota covering about 0.5 sq mi, the 780th-largest of the 960 lakes SwimZone monitors in Minnesota. Satellite imagery detected no blue-green algae bloom as of July 19, 2026.

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, Hart Lake has reached blue-green algae advisory levels in 2 of them, most recently in August 2023. Blooms here have been occasional rather than annual. Its highest recorded reading was 2,979,223 cells/mL in August 2023.

Is it safe to swim in Hart Lake right now?

Hart Lake is clear to swim today. Satellite imagery detected no blue-green algae bloom as of July 19, 2026. Conditions can change quickly with wind, heat, and rain, so check the posted signs and look at the water before you get in.

Does Hart Lake have blue-green algae (cyanobacteria)?

No blue-green algae bloom is detectable at Hart Lake as of July 19, 2026 (below the satellite's roughly 10,000 cells/mL detection limit). Cyanobacteria can still appear within hours in warm, calm, nutrient-rich water, so look before you swim.

Can dogs swim in Hart Lake?

No bloom is detected at Hart Lake today, but dogs are much more vulnerable to blue-green algae than people, and blooms can form within hours. Always keep dogs away from water that looks green, scummy, or discolored, and rinse them off after swimming.

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

Over 7 summers of satellite monitoring since 2020, Hart Lake has reached blue-green algae advisory levels in 2 of them, most recently in August 2023. Blooms here have been occasional rather than annual. Its highest recorded reading was 2,979,223 cells/mL in August 2023.

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