You adapt. Your body can get used to temperatures. You also change your behaviours to suit. Also your schedule changes to suit the weather conditions.
I've acclimatised a fair bit to the UK but when I go back to the Med within a few of days I'm completely settled back into the weather makes me realise how it never really gets that hot in the UK.
Some people I guess can adapt to it, I'm defo one that know wouldn't.