It may be hot, but don't let the dog or the kids swim in Hamilton's Lake Rotoroa.
The warning comes after a sample test by NIWA confirmed algae which can be toxic has reappeared in the lake.
Hamilton City Council's parks and open spaces manager Sally Sheedy said further tests would be done as the sample exceeded safe measurements.
''In the meantime, members of the public are advised to keep out of the water, and parents should not allow their children near the lake's edge,'' Miss Sheedy said.
''Dog owners should also keep their animals away from the water, and fish from the lake should not be eaten.''
Dogs exposed to the water should be taken to a vet as soon as possible, and people who come into contact with ''visible scums and areas of discoloured and turbid water'' should remove wet clothes and hose the area down.