"She said she was looking at rehoming a couple of the puppies, but I offered and she said 'no'."
One of the car's windows was open about 15cm on Friday morning, Young said, but it was "really hot" in Hamilton and she was worried about the dogs' welfare.
"I just want them out of the fricking car," Young said.
Young found out about the dogs when someone alerted the rescue charity to the situation.
"The complainant said they'd been living there on and off for weeks," she said.
"The SPCA wouldn't help ... we get a lot of calls from members of the public when the SPCA won't help."
The dogs, four puppies and their mother, were initially living in the garage at the Enderley property, Young said.
They had been moved to the car after a complaint from the landlord.
Midgen said the dogs were only there while their owner is "dealing with a family situation".
"The dogs will be back to their normal housing - outside of Waikato - next week," she said.
"If our inspectors have any further animal welfare concerns then they will follow up."
Young was an SPCA inspector until 2015, she said.
She also called Animal Control, who gave the owner until this week to register the dogs.
The Waikato SPCA only reopened in February after closing in December 2016 due to financial problems.