Whenever we see depictions of viking longships, they never show any kind of shelter to protect sailors from bad weather. Obviously they must have used something. Is it known or speculated as to how they dealt with this?
More can always be said from anyone with the knowledge, so if anyone wants to speak about Viking ship design, don't let this post stop you! For the meantime, OP, you may be interested in u/jschooltiger's consolidated answer on Viking ships.