I live in the southwestern USA, and have no air conditioning. I do have a solid brick house that is an awesome insulator. So we open up all windows and doors at night, and close the house up tight when the sun rises, putting heavy curtains over the windows. It still gets warm - up to 85 degrees inside on a 100+ degree day, but you get used to it.
It wouldn't work on all the suburban homes around us. The walls aren't insulated enough, there are so many windows that you'd never get them all covered.
I sincerely hope that my future places of work and residence will not regularly subject me to 85 degree interior temperatures on the assumption that I will "get used to it" -- which I strongly suspect actually means "live with it."
I spent a summer at those interior temperatures without AC. I stopped "noticing" it, but my subjective ability to focus and objective running & flash-card-app performance did not recover until the temperatures did. How long does it take to "get used to it?"
A couple weeks, according to folk wisdom, which matches my anecdotal experience.
I'm curious if you went home to cooler temperatures, or if your whole summer was spent in warmth? I definitely have experienced harder times going back and forth vs. always being in the warm environments.
I spent the whole summer in warmth, days and nights. A couple weeks is what it took me not to notice it anymore, except insofar as it affected my performance. That's what I meant by "live with it."
I spent Christmas in Florida and noticed that many people who lived there seemed to find temperatures in the 70s chilly enough to wear a hoodie or something while I had just a t-shirt on.
Conversely, I've noticed that when it first gets cold in NY, it's very biting and unpleasant, while late in the winter, the same temperature doesn't bother me at all and near freezing temps actually feel a little warm.
So I find that the timeframe for me at least is more than a week or two, but no more than about 3 months.
It wouldn't work on all the suburban homes around us. The walls aren't insulated enough, there are so many windows that you'd never get them all covered.