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?
It’s actually not that bad on the equator. Here in Malaysia out temperatures fluctuate between 26-34C during the year. The bits slightly off center are the dangerous ones, with temps in the middle east reaching 50C sometimes.