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?
Malaysia:
You wake up early for outdoor stuff, like jogging or longer dog walks. I do that between 5.30 and about 7.30 (=sunrise).
Other activities throughout the day are indoors mostly, shops, malls, gyms etc. are all airconditioned.
Most homes that have a garden come with a roofed porch area with a ceiling fan, so that keeps sitting outdoors manageable except for maybe the most intense mid-day heat.
Houses here are also solid brick & concrete constructions, and retain cold air better than the wooden constructs you see in the US and Canada, so you can actually keep homes at bearable temperatures without racking up electricity bills.
That’s what got me thinking about this question initially; the home construction. I understand there’s a lot that can be done tree cover, air flow, and decent thermal material, unfortunately it seems that’s often deemed too expensive in places that aren’t consistently warmer.