The way you experience temperature heavily depends on the relative humidity.
E.g. I find 0C in London way colder than -15C in Northern Europe.
E.g. I find 0C in London way colder than -15C in Northern Europe.
I also think that you wear different clothes and are more prepeared when it is -15.
It's not _just_ humidity. Rain just simply can't exist at -15C, so you can't get your clothes moist because it can only snow, and that snow is cold enough not to stick to you at all.
I am not even going to start on the fact that you can walk miles of snow and not get wet, while walking through miles of slush... Well, I hope you understand the distinction.