In Northland, seven have been rescued so far this summer compared with six for the same period last summer.
Between December 2014 and January 2016, a total of 22 children and 21 pets were rescued in the region.
Most were in central Whangarei, at 26, followed by Warkworth where six were rescued in the 13-month period.
Dr Tuck said children should never be left unattended in cars for a number of reasons.
"They don't just potentially boil to death but the more mobile and mischief they can get up to, the more harm they do."
He said there had been instances where children have released handbrakes or have been abducted by people who stole vehicles and later realised the little ones were inside.
"In Northland, a child inside a car with windows up can get into serious health risk within half an hour. As soon as the temperature gets into the 40s muscles in the body start to break down. Don't underestimate how quickly the inside of the car can become lethally hot," Dr Tuck said.
AA national road service manager, John Healy, said the upsurge in incidences was deeply concerning. "These types of lockouts are happening far more often than people think."
Last year, 1500 call-outs were for a child or animals at risk because they were either consciously left in a vehicle, or car keys were accidentally lost or locked inside.
Mr Healy said some people thought leaving windows slightly open would alleviate the heat but it was not a safe alternative.
To call the AA in for emergency assistance, dial 0800 500 222 or *222 from mobiles.