"Algal blooms can develop rapidly and unpredictably and can sometimes produce toxins that are harmful to people, as well as animals," Miller said.
"The current warm conditions are perfect for toxic algae growth, so it is always safest to check the water before you get in. Look before you leap."
Miller said if the water looks discoloured, smells unusual if there is scum on the surface, or the water has green or brown particles suspended in it - then it was best to avoid contact with the water and swim or play somewhere else.
From the beginning of December to the end of March, Waikato Regional Council will be checking for signs of E.coli, as well as cyanobacteria (the micro-organism that causes potentially toxic algal blooms).
In the meantime, additional sampling will be carried out as required if alerted to potential problems by members of the public.
Report any concerns by calling the Waikato Regional Council on 0800 800