Weather in Alaska or Vancouver North along the coast can change quite a bit. You do not say where you are from and your tolerance for colder weather. General speaking you need to pack for travel outside with layers. it can be quite cool on the water around the glaciers. And it can rain off and on. Early and late season can be chilly. June 21 is the longest day and you will get lots of sunlight 2 weeks either side of tht date and more warmth can be had into July & August. So a warm tshirt. A sweat shirt and a jacket of water/wind proof over everything. Jeans gets you though most of the worst days. But when the sun is out it can be hot. Vancouver has great beaches with the odd Palm tree around town. I twice now have gotten a tan in Ketchikan . (different months) You just have to be ready for anything. But unless you are from somewhere south that never drops below 70 F prepared as above you will be fine. Footwear> lightweight good walking shoes you will be fine. Onto glaciers is a different matter and most operator/tours have boots available or clamp ons. But check with tour/operator before you book. Toques may be worn on any given day near the glaciers. I have seen ear muffs on some some of our southern visitors.. I was caught unawares once in Skagway with out my top layer . It was windy and cold. But I survived.. Hope that helps.
I see in another thread you are going in June. It may be lighter towards the 21'st but you will have more chance of have a ccol cruise. Less chance of fog than later in the season.