The Atlantic coast is typically much warmer than inland Finland, but chilly wet winds can be tough nonetheless.We are hoping to make this a 2 months northern Scandinavian trip. The cold will be a challenge π
Regarding your earlier question about routes to drive, in general all major roads remain drivable throughout winter. There can be temporary stops of a couple of days after heavy blizzards, but Google maps should be able to tell which route is passable. the official site for Finland is Liikennetilanne and for sweden Trafikverket.se