Anyone tempted to cool off in a South Canterbury river as summer heats up has limited options.

Five locations in the district remain out of bounds after high levels of toxic algae were detected, making them dangerous for people and their pets to swim in or drink from.

That warning includes three locations at the Opihi River – near the Wapiti Huts, the Saleyards Bridge at Pleasant Point and next to State Highway 1 at Temuka.

Warnings are also in place for the Waihi River near the Wilson St footbridge in Geraldine, the Waihao River near Birdhouses Rd, Saltwater Creek at Canary Rd and the Centennial Park pond in Timaru.

Canterbury medical officer of health Dr Cheryl Brunton said the algal mats detected could produce toxins that were harmful.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips,” she said.

“If you experience any of these symptoms, visit your doctor immediately, [and] also let your doctor know if you’ve had contact with dark brown/black algal mats or water in this area.”

She advised people not to drink the water from any of the affected rivers at any time because boiling the water would not remove the toxin.

An online tool called Can I Swim Here? was launched late last month to inform people which rivers, lakes and beaches were safe.

The tool, which was launched by Land, Air, Water Aotearoa, shows the most up-to-date water quality information for nearly 100 sites across Canterbury and is available at SneakersSneakers