Waiata's mother was also sleeping in the van on the morning of December 20.
According to the coroner's report, she was cold and lowered the driver's window by less than an inch.
She gave Waiata a bottle at some point and was awoken by her partner knocking on the van's window about 2.30pm.
They checked Waiata and found that she was unresponsive.
Emergency services rushed to the scene but were unable to resuscitate the 4-month-old baby.
Thermal testing of the van was undertaken the next day.
According to the coroner's report, when the gauge was checked shortly after 3pm it recorded a temperature of 42.9°C.
Coroner McDowall said babies and young children were less able to regulate their body temperature which made them susceptible to hyperthermia in a short period of time.
"That is, babies and children left in hot cars are at risk of heatstroke, dehydration and death."
Even at relatively cool ambient temperatures the "temperature rise in vehicles is significant on clear sunny days" and puts infants at risk.
"Vehicles heat up rapidly, with the majority of the temperature rise occurring within the first 15 to 30 minutes.
"Leaving the windows opened slightly does not significantly slow the heating process or decrease the maximum temperature attained."
The coroner deemed public education efforts seemed necessary to decrease fatalities in this situation.
"Accordingly, I propose to send a copy of this finding to Safekids Aotearoa, a service of Starship Children's health, whose mission is to reduce the incidence and severity of unintentional injuries to children aged 0 to 14 years.
"As recognised experts in unintentional child injury prevention, Safekids is well placed to give consideration to raising awareness of this issue and how best to promote safety messaging."
Police confirmed no charges had been laid in relation to Waiata's death.
