Stanford University School of Medicine have found that temperatures inside a parked car can raise significantly if the sun is out, even if ambient temperature is average.
The effect is similiar to a greenhouse effect, warming up a mass of air trapped inside glass. Which is what a car becomes when it’s left parked under the sun.
A small open crack in the windows or air conditioning did not help with slowing down the rate of heating. slowing down the temperature spike for about only five minutes.
So people, don’t leave your pets or children inside your car, even if you are only making a short stop.