This is really true. Where I am from, we discuss a six-week period or so when the season changes, from shitty to other-shitty, in which we say either your blood

This is really true. Where I am from, we discuss a six-week period or so when the season changes, from shitty to other-shitty, in which we say either your blood or skin thickens to the cold, or your blood thins for the warmth. (somehow, the skin never thins) I have no idea if this has any scientific basis. Anecdotally, the partner of the Columbian who shares an office with me is complaining that she is now used to colder temperatures.