Having lived in both humid and dry climates, the critical factor for me is humidity. I'd rather be in an area where it's 110F and dry than 95 and humid.
If the heat index is over 90 it is too hot for comfort. The past week the heat index has been around 110f/43.3c in my area. (actual temp in the high 90's with 90+% humidity). The perfect outside daytime temp is 75f with low humidity.