glowingfish

That is a great question!
Because wet and cold and dark have a lot to do with it. So 10C when its dark 16 hours a day is harder than -10C when its dark "only" 14 hours a day.

Another thing is, as far as the danger of the cold---skin loses heat something like 40 times faster when it is wet. So the temperatures around -2 to 2C are actually more dangerous than -10C, because they are usually warm enough where there is rain mixed with snow, and it covers your clothing and gets them wet. Sometimes, even down to -10C or lower, it is really dry, and as long as you are insulated, you are safe, more or less. But the mushy slushy cold that happens right around freezing can be very dangerous...and even when it isn't, it is miserable.