Do we know if White Harbor is a warm-water port or not? It’ still unfrozen as of ADwD, but I think that’s still technically late autumn?

I would guess that Wyman wouldn’t build a giant fleet on the verge of winter if he knew that his ships were going to get frozen in. 

And it would make sense, given that White Harbor is about as south as the North gets, if it was the one port in the North that didn’t freeze in winter.