I think it is a case of what you are used to since our current daily temperatures in mid winter are in the mid to high teens and everyone is complaining about how cold it is ! In summer, our temperatures In the low 30s are very pleasant and only when they reach the high 30s are we uncomfortable. Last summer we had a high of just on 47C and that we REALLY complained about.
During the summer I usually get up early and open all doors and windows and turn the ceiling fans on before sunrise to let the cooler air flow through the house (front faces south and the back north) and then close the house up again when the sun rises - including the curtains, blinds and interior doors. Earlier in the year I invested in a portable reverse cycle air conditioner which can be moved from room to room for cooling in the summer and heating in the winter. It has been one of my best investments !