Several things determine actual danger in relation to a pet. The vehicle can be 100 degrees inside and the pet be safe as long as there is ample water. The type of vehicle also is a huge issue in what the actual inside vehicle temp is. I locked horns with Knoxville Animal Control years back over that very issue.
Some Peek-A-Boo self appointed KOOK was peeping into parked vehicles looking for her rescue. I had seen the woman at the location before but didn't put two and two together until this. My dog was inside a conversion van that was well insulated, tinyed windows with curtains, and had ample and highly visible to anyone looking in supply of water I kept up at the engine cover cup holders. The temps that day were upper 70's low 80's under mostly partly cloudy skies. I also had an inside thermometer in vehicle.
We were gone a while as I approached the van I saw a woman jump in the passenger side of an animal control truck and jump out at our vehicle then take off. The dog was in fact panting AND BARKING as she does when persons are pecking on the window of the van harassing her. Plenty of water was available and about a third of it drank. Inside van temperature was 90 degrees which is safe for man and beast if a persons thinks about it. BTW I had checked on the dog. I showed the animal control officer the thermometer right off, the dog was still much more interested barking at strangers including the A/C officer than any heat distress, the officer wanted to cite me but I had broken no law nor endangered no animal.
Now our dogs are pampered. So to be a law abiding citizen I called the A/C supervisor and asked if it would be OK if the dog was in the vehicle as long as the A/C was left running. I got a nice long lecture about City Code and sub-part ordinance of whatever regulation saying no vehicle shall be left unattended and engine running with the city limits of yada yada.. Then the conversation became more intense.
I reminded the supervisor many persons traveled with pets and stopped to eat or at a store thus pets were left in running vehicles with A/C anything from vans to RV's and that if they wanted to make a huge bust they could go to the nearest truck stops and find pets inside running trucks.
I exercise reasonable caution. I was doing so that day as well. On a questionable day the dog that likes to ride stays home unless it is a place she can go in also. I also now do this now for Kook Insurance. I place a GMRS radio in the vehicle placed in voice activated mic mode. The bark triggers the mic and I hear the dog barking. Yea I've caught one one or two Animal Precient Patrol Wannabees harassing my dog to get her worked up before making a call. Yes some kooks are that sick in their heads. There is obvious danger noticed by passer bys which deserve attention then there are certifable KOOKs.
I DID say ‘dumb sons-of-b*tches; not Freepers. :-)