We traveled on RCI round trip from Baltimore to Quebec City several years ago. Our first stop was at Bar Harbor. We opted for the all day trip to Acadia National Park and Cadillac Mountain. The sights are not to be missed from the top of Cadillac Mountain - it was a clear day. The bus trip was too long and didn't allow for any wandering time in Bar Harbor, which we would have loved to explore. In Halifax, NS, we took a walking tour. Our guide, dressed in a kilt, took us through gardens, toured the Citadel and on to the Maritime Museum of the Atlantic where we learned about the city's role in the Titanic disaster. In St. Johns, NB, we also did the walking tour that visited the City Market, gardens and a church. Quebec City was very cold that 3rd week in Sept. We did the combination walking and carriage tour that passed the Fairmont Le Chateau Fontenac. A must see is the trompe-l'oeil Quebec City Mural. Sailing home, our ship went up the Saguenay River. Make sure you are on deck to watch the scenery and look for whales. Our final stop was Portland. There we took the tour out to Cape Elizabeth. The wild roses were in bloom and the shrubs covered with bright red rose hips - a very beautiful spot. We enjoyed free time to wander around the town after our tour.
As to weather: Our cruise caught the tail end of a tropical storm so the seas did get rough for a few hours. For the most part the seas were slight. We did encounter cold rain. I believe it was in the low 40's some mornings. The trees hadn't begun to change colors yet though. Things we needed were rain gear, sweaters and gloves. Of course, weather may be completely different while you're there. It was only after looking at our pictures that I remembered the cold and rain. Our memories of that trip are filled with light houses, ocean views, blue sky, beautiful scenery and friendly people.
Enjoy your trip!