This is our first trip to Alaska. Sailing on Star Princess from Seattle on May 17th; what should we pack for this time of year; also going to Whistler Canada after cruise is done so packing could be tricky (as I assume Whistler will be much warmer than Alaska?)
Actually May In Alaska and Whistler will have a lot in common or could. The mountain has it's own weather as does the coast.
You won't have to pack anything extra for either. The secret is layers. T shirt/Sweater or sweat shirt, rain proof outer shell, a light one is fine just adjust what you wear underneath that's all.
Could be sunny in both places or cool and cloudy with rain. No one knows for sure what will turn up. The weather you get is generally what you see when you wake up It's like that along the coast all year.
I'm not sure how far north your ship goes on your itinerary but if it's the usual Seattle return to only Ketchikan/Skagway and around there that's only half way up the Province of BC and not all that far north really. Check a map
On any Alaskan cruise you want to dress in layers. There is a good chance for cool weather, rainy weather, hot weather and sunny weather. The hardest part about cruising Alaska is you must have clothing for any type of weather because there is a good chance you will see all types of weather.