Last year I was sailing in Cape Breton the whole month of November. I was almost the last boat out of the St. Peter's Lock before they closed it for the
winter (I was out on Thursday, closed it Friday).
You would not want to sail earlier on the south coast of
Newfoundland. It is fogbound the whole month of July in the mornings, and sometimes even the afternoons. I do admit that the winds are very strong in October and November and will have to pick a good window for the return.
My home port is
Wood Islands PEI. They run the
ferry up to a week before
Christmas. There is rarely any ice before that.