Last week we had -28c, I would say that -30c at most. Some winters it can get up to -35-40c temporary, but it's not that common nowadays. But overall, it's pretty cold, for plants, not for me
I used to live near the arctic circle, and there is a bit colder. Now I live in the "South", the spring begins much earlier, and it's not that dark at mid-winter, summer is warmer and so on..