People and their dogs are being advised not to swim in Lower Thetis and Prior lakes because of a blue-green algae bloom.
Ingesting the water could be harmful to your health, and potentially fatal for your pooch.
The Capital Regional District issued the notice this week in consultation with Island Health.
Blue-green algae can produce cyanotoxins that can cause headaches and abdominal pain in humans and lead to lethal liver damage in dogs.
The algae usually produce a visible blue-green sheen, which appears as surface scum. But not all blooms are easy to see, and toxins can still be present in the water even if you can’t see the blooms, said the CRD. Blooms are unpredictable and may occur at any time.