I mean, those places didn't have air conditioning 50-100 years ago and did fine, now air conditioning is life saving devices there. Global warming/climate change is real.

The WHO guide others are posting says fans only work under 40C, but that's the absolute maximum. There's no other option than resorting to devices based on refrigeration cycle when people are already dying("estimated through excess mortality" or however you dress it up), beyond being useless(human cognitive performance significantly degrade at above 28C).

The upper bound of 40C quoted in other comments is also just absolute maximum temperature - it's just saying that there's no way fans do anything if temperature of air and body are actually equal. The practical upper bound is lower than that(humidity and metabolism dependent, I guess).