How hot is too hot??

I live in Phoenix and it was obviously hot today...about 102F and we drove to see my inlaws about an hour south. It was still very hot there and humid. My father in law is kind of mentally nuts and he hates air conditioning. My LO is 12 weeks and their house was 85 degrees! Amelia was sweating a lot and we were there for 6 hours and the last 2 she was super crabby and I think it's bc she was so hot! Is it bad for her health to be in that heat?! We have to go see them again next weekend and spend the night 😫 it makes me so angry! My husbands dad can be such a jerk sometimes! Let everybody be miserable including a 3 month old infant bc you don't like air conditioning for no reason. Arrgghh!