I will be in CT for first time oct 28, how often is boat service canceled due to rough seas
I can't give you a count but when we were there at the end of May a year ago, the service was not running for two days because of rough seas. Then, on the third day, it was beautiful and we got to ride the ferry. However, the seas were still rough enough that the ferry only ran from Monterosso to Portovenere and back. No stopping at, or pulling into, the other 4 towns.
Frequently enough to never plan on it being available. Luckily, you may always depend on the local train or bus service.