We get aclimatized to hot and cold. It is generally the rapid changes in temperature, one way or the other that causes the problems. For example, I lived in Papua-New Guinea for two years where the temperature ranged between about 70 F to 82, max 84. Then I came home to Australia in Aussie's mid summer. It was around 90, pretty warm I thought. Then the temperature dropped to around 50 that night and I felt very chilly.
On the other hand, I spent a year on sub-Antarctic Macquarie Island. When we expeditioners arrived there we were clad in thermal underwear, woollen shirts, jumpers, windproof parkas, three pairs of socks et cetera. We wondered why the guys we were relieving (the outgoing team who'd already spent a year there) were wearing just open necks shirts and pants and beanies. But after a while that's how we, too, dressed on those occassions when the wind dropped.
Calm days were rare,of course, so we usually took our windproofs and wrapped up well if we were leaving the safety of the camp.
If you live in the tropics, your blood thins out. If you live perpeturally in the cold it thickens up. However, here in Sydney where I live the temperatures fluctuate considerably but, in the main its a good average temperature with only a few days too hot (above 85 - yes and it can go up to 110 or more. But this is rare) and a few days just a little cold. Say 40 with the occassional drop below freezing (32 F)
I've never seen it snow in Sydney. Though it does snow up on the mountains (about fifty miles) away for a few days of each year as a rule