We sailed from Vancouver on the Volendam last year on 14th June. We always had to have a light jacket on when on deck and when in the area of the glaciers had to put a fleece on top of it, and my husband wore a hat. Otherwise the weather was clear with sunshine and only one day of rain when leaving Vancouver. I think the best idea is to wear layers. Maybe in August it will be warmer. It is a fantastic trip, good luck.
Pack sensibly , you will need layers when in The Glaciers and light clothing on Board.
It rained more in showers than anything.
We travelled out of Vancouver last week, you are in for a treat.... the scenery is unbelievable....
We travelled on RCI, but saw two Holland America Ships, they looked very Grand!!
We travelled with Holland America to Alaska last year in August. The weather was sunny but cold. Wear layers and sensible shoes. I didnt think to take a hat and scarf and ended up buying one out there. It is probably my favourite cruise. The views are breathtaking. The ship and service fabulous. Have a fantastic time.