Waikato police are urging people not to leave kids or pets in cars.

Two pre-schoolers had to be rescued from a car at The Base shopping centre in Hamilton yesterday after they were left there by their grandfather, who'd gone to get takeaways.

It was around 30 degrees outside and could've been 10 degrees hotter in the vehicle.

The children had to be rescued after they became agitated.

Senior Sergeant Simon Cherry said no charges have been made against the grandfather yet, but police are looking into that possibility.

"A referral's been made to our child protection team which deals with specialist child abuse cases and the work very closely with the ministry for vulnerable children."

The grandfather was also taking care of three other children that day, who were at a swimming pool.

Cherry said the message is quite clear when it comes to children, pets and anyone else in a car.

"It's not to leave them in the car, the car can get very hot very quickly and [it] could end up with some very tragic circumstances."

Cherry said the two pre-schoolers were cooled down with wet towels and ice and recovered quickly.