How much can a koala bear? One was captured on camera getting a cool drink in Adelaide after record-breaking temperatures.

The city broke the record over the weekend for its longest December heatwave on the books, with four consecutive days over 40 degrees Celsius.

Paul Jansen was driving along Valley Road in Hope Valley on Sunday morning when he spotted the koala on the side of the road.

He said the area had received some much-needed rain about half an hour beforehand, and a lot of the rainwater had been flowing down to the drains.

Mr Jansen said it was "phenomenal" to see the koala drinking water for so long.

Paul Jansen said the koala had been drinking for about 15-20 minutes before he had to leave. ( Supplied: Paul Jansen )

"It was lapping the water up for about 15 to 20 minutes," he said.

"I've had dogs before that would lap up water for one to two minutes then be on their way again, so the koala must have really needed a drink."

However, Adelaide Koala and Wildlife Hospital director Rae Campbell said the koala might have been drinking a lot due to a much more serious issue.

"South Australia is the only state where the koala population suffers from renal failure," she said.

"If people observe them drinking a lot, they should call us and we can go out and get the koala for further testing."

Treating 'wall-to-wall' koalas over the hot weekend

Ms Campbell said koalas would source water from "wherever they can get it".

"People believe that koalas don't drink — of course they need to drink," she said.

She said her small team of volunteers was flat out over the weekend treating koalas for heat stress, as well as dog attacks.

"There were koalas coming in just all the time, it was wall-to-wall koalas," she said.

Ms Campbell said the dog attacks might also have been due to koalas coming down from their trees to source water.

"We encourage people to leave a shallow container under trees so they can get a drink without wandering too far," she said.

"If people have a swimming pool, it's good to leave a rope with an empty bottle tied to the fence and leading into the pool — koalas can swim but they can't get out of the pool.

"And if you see a koala looking like it needs a drink, you can also spray it with your hose."