I have cycled 12km everyday to school when I was young, but it was on flat roads. In winter it was sometimes -5 to -15 and around those temps, sometimes I would fetch a ride, because I agree, in winter it can be harsh, but other then that, it was biking every day.

Rain is even worse than snow by the way. Wind is also killing. But if it was a snowy day with not much wind, cycling is actually fun.