Translation:The weasels cannot climb into the sky.
Climbing in the sky requires a foothold in the sky, which is not possible. Climbing to the sky requires a ladder or an elevator, and is achieved when you become really high up. Climbing into the sky, like climbing to the sky, requires a ladder. Once you're pretty high up, you could correctly say "look at me, I climbed into the sky!" Just, don't fall while you're up there... Climbing the sky is not possible, because it is the sky. There are no hand or foot-holds to use. Climbing up the sky requires the sky to be a vertical 2D surface, which it is not. So no, that wouldn't work either.
is this the rule for the English ? I would have thought that 'in the sky' is as good as the same as 'into the sky'. With the latter maybe more of a motion (of floating, drifting, etc) that takes some time. Whereas 'in' is done in an instance. the moment you are in you are in....