A baby and a young child were found distressed and sweating profusely after being left locked in a hot car in 33-degree heat while their mother went shopping.

Napier woman Chrystal Alatasi discovered the children hot and distressed inside a car parked at a Napier supermarket carpark yesterday.

Alatasi had just finished loading her groceries into her car when she heard a baby crying.

Being a mother-of-four, the Napier woman is well versed on the difference between a tantrum and a distressed cry so she immediately knew something was wrong.

The crying was coming from a black car with dark tinted windows across a pedestrian crossing in the car park, not very far from where Alatasi had parked.

The children, approximately aged 2 and 5, were left locked in the car. Photo / Supplied

She approached the vehicle and had to look really close to see through the very tinted windows.

There were no adults in the front but she spotted a baby and a toddler in the back, who were both showing signs of distress, with the temperature at 33 degrees.

A desperate Alatasi tried every door, but the car was fully locked. She called 111 and thought she was going to have to smash a window.

The emergency calltaker suggested asking the young girl in the car if she could unlock it from the inside. The girl reached for the lock and managed to do that, following Alatasi's instructions.

"It was like opening an oven door," Alatasi told the Herald.

"A blast of heat came out as the car door opened.

"The two children were dripping, sweating profusely, with red cheeks, and crying," she recalls.

"It was shocking, that baby was in the full-blown sun."

Chrystal Alatasi managed to get the girl to unlock the car. Photo / Supplied

The two children had water bottles on their car seats - but the baby's bottle had fallen down, Alatasi says.

The woman asked the girl, who told her the family was from Dunedin and holidaying in Napier, to climb over to her baby brother's side of the car and unlock his door as well.

She didn't want to get them out of the vehicle but wanted them to get the fresh air they desperately needed.

After a few long minutes, Alatasi says she spotted the mother coming out of the supermarket, the New World in Greenmeadows.

"She was looking at me funny. I was so upset and angry, I was shaking and crying," she says.

"She wasn't rushing to the car. That's the unfortunate thing.

"It's absolutely disgusting! I had a go at her, she said it was a mistake but that's not a mistake!"

Alatasi says she stayed behind the car while waiting for police to arrive. She isn't sure how old the children were but estimated the boy was two-years-old and the girl around five-years-old.

Once police arrived, Alatasi left, still shaken by the incident.

Police gave the mother a warning. Photo / Supplied

She took to social media to express her "disgust" at the situation, and says that "in this day and age, parents should know better". She has no doubt the children's lives were put at risk yesterday.

Police has confirmed that "a report of children being left unaccompanied in a car in Napier was made just before 5pm yesterday".

"The offender was given a formal warning and a report will be made with Oranga Tamariki."