Approx. 1/3 of territory is covered with deepfrozen soil ("eternal frost" in russian). But 70% of people live in places with european climate, maybe a little harsher. 15-20% of the rest in more continental where it could be -40 in winter and +35 in summer.

The myth of extreme cold started during two wars - Napoleonic and 2nd WW when armies unprepared to winter conditions march deep into russian territory and found themselves in quite a poor conditions. The result would have been the same in any other territory with such an approach.