Funny Donna, always a good bit of humor and I love the car simile
( don't forget to have the fender skirts hemmed!).
Seriously tho, Its OK if say he is in an A/C's appt and you need to take him to the vet and outside temp is like in the 90's. THat little bit of time from the house to the car is not going to hurt him. But an abrupt sustained change from cold to hot, like from an A/C'd home to an outside cage for the afternoon and then back into the cold house, thats when its not good. So my good pal 'Boats is 100% dead on ( as usual). And drafts - so don't place his cage or playstand directly in the air stream from the A/C unit, or place it where the cage is in direct sunlight where the heat will build up, even in an A/C'd room. Common sense should give you a better idea of this. The rule we follow -- if its comfortable for you, it should be OK for your parrot. to a certain extent
I always check the feathers between Salty's legs - if they are kind of shivering, he is cold. Like us, parrots are able to maintain body heat to a certain extent, within reason. Shivering, either of feathers , fur or skin, is how warm blooded animal bodies generate a bit of body heat, but doing that continuously, every day, all day long, uses up energy.