Just returned from our cruise to Alaska and what warm temperatures we had!! First port everyone was trying to find summery things to buy as they had packed way too warm!
Definately take light clothing you can layer up IF you need to. Even on our Glacier viewing days I found myself seeking some "shade". Nice though...78 to 83 the entire trip! Calm seas, lots of whales, orca's, seals and bald eagles...wonderful!!
Juneau hit low 90's the day before we arrived and was 83 when we docked.