We went on the same trip last june.our suitcases weighed 32kg with all the extra thick clothes!from banff to vancouver the weather was pleasant but never shorts weather.we have waterproof coats with zip out fleeces inside which were invaluable as there was snow when we went up the chairlift in lake louise,we even had snowball fights!The only place we had bad weather was glacier bay where it rained solid all day and i even put my gloves on which i had taken as a joke but it was off the best days of my life with the glaciers constantly creaking and falling into the sea!the hot pea soup served on deck went down a treat!by contrast when we got to skagway it was 75! so lots of layers is the answer have a great holiday we're planning to do it again in a few years enjoy !
There are places where it will be really cold, some places will be wet and others will be sunny. Take anoraks, sweat shirts / jumpers and shorts. the answer is you must be prepared for cold and wet but be able to peal off layers as well. Great place to go though .... Nei.