Any temperature below -15?C during the winter is simply enough for me to avoid getting outside of my house like a plague. Problem is, they often always come with wind chills that are usually under -20?C, which is already too cold. That doesn't bode too well for me, because I'm living in Canada, which is pretty much a freaking freezer.
Anything below 40?F is cold to me, which strikes some people as odd because I live in Arizona and was born here as well. I think I was meant for a colder climate.