I haven't read the whole thread, but I am so tickled that I'm not the only one who quickly forgets what certain temps feel like, and how to dress for them! I have even thought that it would be smart to write down the weather conditions for each of my outfit photos, for reference later.
It's only just heated up to 80s here in Boston, and all of June was in the 60s, so my memory has not yet faded. I would say that there is a warm 60s, and then there is a cold 60s. The type of 60s we had in June was more on the warm side. Please, DO check accuweather's "Real Feel" - that will give you an idea of which sort of 60s you are going to get. Humidity and wind make a big difference. High humidity will make it feel warmer; a stiff wind coming off melting ice or the ocean will make it feel a lot colder.
If you suspect a warmer 60s, then I can assure you I made out just fine last month in lightweight clothes with lots of layers. Cotton cami under a short sleeve top, with a cotton cardigan over, and a jean jacket or rain coat if necessary. No socks. Long jeans were optional (there were a few days I went out in long jeans, but ended up rolling them to clam length). I'd say if you wear long jeans, as a general rule of thumb, you don't need as many layers or long sleeves on top. And vice versa, if you wear more layers/long sleeves on top, you can probably get away with clams on the bottom. As for dresses, I was most comfortable with a jean jacket, cami, and cropped leggings.
The good thing about all this layering is you can easily add/subtract. Remember that weather reports aren't always accurate. If it's been in the 70s, then err on the side of "it may warm up more than they are forecasting."
For chillier 60s, like in the fall, I would opt for long sleeves, jeans, socks, covered toes, and even thicker blazers. I doubt this is what you are going to get, but I could be wrong. I've never been to alaska or on a cruise. I imagine that wind chill will be a big factor. A trench coat might be worthwhile, as it will cut the wind chill and yet it is nicer than a gear-coat.
Pashmina for night time dinners on the boat!