It is whatever you are use to for sure. I have been in Tampa , Florida at a hotel right next to ocean in September , I stepped outside and I might as well have jumped into a shower. I think the temperature was only around mid 90's F but the humidity was unbearable, I would take a -40C here over that any day.
Backup heater yeah most of us have space heaters and or fireplaces so in a pinch it will do. Extended periods of time without the furnamce working in extreme cold will lead to a whole other set of home reapir issues.
I have also been in Arizona desert (between Palm Springs and Phoenix) and it was well over 100 (also been in Vegas in July just over 100). While that is a much drier climate still outside was stifling.
So I guess +40 with AC and -40 with a furnace and Fireplace is all comfortable
I guess my point was preferring -40 over +40 would pertain to being outside. I can dress for -40 there are only so many clothes I can take off for +40
Leaving with either extreme for extended periods of time is not for anyone I would guess.
Suppose to be +2 here Friday a 50 degree C change in a few days ...impressive what
I usually get to Stu's area evey July and indeed beautiful country and almost always between 25-35 with lots of Sun