I live in a pretty hot climate, but it’s only really unbearable at times due to shoddy building and bad urban planning. Even then, summer can be difficult.
I can’t imagine what it’s like on the equator, especially in dense urban centres. What’s Mumbai, Bangkok, or Singapore like at the height of the wet season?! How do millions of people function day to day?
Water, inside and out. Dune (the book) had a great quote about the best place for water is inside you.
Humans evolved to deal with heat, and yes, later cold, but our roots are in Africa. So many ways to cool with water, you find strategies that work. Misting is a great example. Low power and water use, works outdoors, they use it in the NFL.
I use gaiters year round, dry for cold, wet for heat. They can make a dramatic difference. Wrap an ice cube in one, put it at the base of your neck, fool your brain stem into thinking you’re cooler.
Staying small is huge (heh). The square cube law is a thing. If you took my skinny hide and spread it out on top of a tall fat man, it would be fairly close. But our volume would be drastically different.
Being fat in hot climates is miserable. Had to take a shower after going to get the mail in the summer. In the mid 40s(5-8C?) and I’d be going around in a long sleeve shirt. By the time I should start to get cold, my body’s warmed up or I’m in a conditioned place.