SIGNS warning of a blue-green algae outbreak have been positioned around lakes Guthridge and Guyatt in Sale.
The alert has been issued after testing of the water in both lakes detected levels of algae that could pose a threat to pets if they swim in it.
The water level in Lake Guyatt is quite low, and Wellington Shire warns recreational users in the area to keep dogs leads and not allow them to swim in the water.
If a person or animal does come into contact with the water, they should wash immediately with fresh water.
Blue-green algae occurs naturally and can reproduce quickly in favourable conditions where there is still or slow-flowing or low water levels, abundant sunlight and sufficient levels of nutrients.
The sustained hot weather and lack of rain have provided ideal breeding conditions for the algae.
Wellington Shire Council says it will continue to monitor the health of both lakes and conduct regular water tests.
For more information, phone the environmental health team on 1300 366 244.