Right now, Dec 17. 2014, we have had several days of +5 or so and 20 years ago, no one would have believed a Christmas with those kinds of temps.
Even in the far north, temperatures have just jumped in the last few decades.
Now for North of 60, your shock will not just be from the -30 or even colder. I remember the first time I went out in -48 and what really gets to you is the 24 hour darkness, the sun kind of creeps up a bit in the middle of the day and disappears.
The reverse is that you get to see the sun above the horizon late into the evening and it's really damaging to your sleep cycle, at least it was for me.
Now, take a supply of Vitamin D, get lots of exercise, lots of sleep and watch out for all the insidious effects of what is called "winter blues" not just by yourself but by everyone else.
Otherwise it can be incredibly beautiful and an experience.
If you are single in some of those locations, you will be regarded as fresh meat so keep the big stick handy..