I think you should be aware of the effect of building design and culture, in addition to temperature and humidity.
I was born and raised in Miami, Florida. The high for today is 30, with 80% humidity. Low is 26. Mumbai's high today is 28, with 94% humidity and a low of 26. Miami is next to the sea, which helps keep it cool. By comparison, Orlando, which is inland, has a high today of 34 and 89% humidity. Kolkata's high for today is 34, with a 67% humidity.
I think fair to say that I have some experience with this sort of weather.
We did not have air conditioning in Miami, unlike most of our friends. My father, who himself was raised in Cuba during the 1950s, thought it was too expensive. And he would be right, because our house was not designed for it. Instead, it was designed to keep cool naturally.
It had high ceilings, so the heat would gather above head level, it had no insulation, the windows were not air tight, and the house itself sat on cinder blocks so there could be air flow under the house. We also had ceiling fans, to keep the air moving.
On the other hand, a house designed for cold weather has insulation, air-tight windows, and minimal surface area, in order to keep the heat in. A house designed for air conditioning does the same, in order to keep the heat out.
Temperatures which would be no problem in Florida would be horrid up north. New York apartment buildings are not designed for cooling. There's no cross-breeze and too much insulation. There's also a lot of stone and concrete in NYC to absorb heat, while Florida has more plant cover. NYC is 3-4 degrees warmer than the areas around it, due to this heat island effect. (It's also why NYC is the northernmost major city on the North American with a humid subtropical climate.)
But there's also cultural reasons. Think of the old stories of the British in India, during time of imperial rule. The British wore wool clothes in that heat, because to do otherwise was "un-British", and as a way to separate them (as part of the ruling class) from the rest of the people in India.
This story even mentions one of the cultural reasons - no one wore shorts, despite the heat. At this time (1920s and 1930s) in New York, it was illegal even for men to be topless on the beach. Quoting from http://www.bikiniscience.com/costumes/soutien-gorge_SS/tople... , "Euro-American confrontation with topless prior to the 1960s are often deeply conflicted and involved a racial separation. This is because the dark-skinned, tropical people world-wide often are topless, whereas their white-skinned northern hemisphere counterpoints wear more clothes."
Cultural expectations run deep. Northerns have a stereotype about the "lazy" Southerners. Indeed, when I moved up north I discovered that I was actually a slow walker, when I used to think I was a bit faster than average. A friend of mine told a story the other way, of someone from Maine, who moved to Florida and wasn't going to give up his northern ways. Only to discover that there's a reason for slow movements the first time he tried to take a brisk walk. As prasoon2211 commented, "you're sweating profusely from the minimal of exertions."
So yes, you're both right in pointing out that "this is a little more than moderately hot for many parts of the world". But temperature and humidity alone aren't the only important factors.
Because by the same token, weather that New Yorkers could handle without blinking - freezing temperatures for a month with dips down to -12 - would have destroyed most of the homes in Miami. All of our plumbing was exposed to the outside, so the water pipes and sewer lines would freeze in that sort of weather. Even the municipal water mains would likely freeze and burst, since they are just below the surface and not designed for that weather.
That sort of cold weather would likely create similar havoc and huge numbers of deaths in most of the cities in India.
For that matter, since we had no insulation, when it was 5 outside, it was also 5 inside. We didn't have the warm wool blankets or down comforters that people up north would use, because it isn't worthwhile to buy and store them for the few weeks a year they might be used, so we piled on all of the thin cotton blankets we had.