We have done a couple out of Vancouver...
Cruised on a Princess from V to Whittier, with land stops in Ketchikan, Skagway and Juneau.
Almost all V based cruises leave from Canada Place, downtown Vancouver on the water. If staying in V before or after the cruise, cop a decent hotel close by. One can walk/pull your luggage across street to Canada Place, elevator up to boat embarkation, etc. Most boarding afternoons are a zoo; be patient.
In V, before of after, get around the town by foot, taxi, rented bike: beautiful city and area, imo, and I have been all over the world.
Land 'excursions' during the cruise range from huh? to OK to pretty good, depending on one's taste and interest.
Whatever cruise company you are on will offer pre-buy excursions when you book. The more interesting ones will fill up quickly. The cruise line offered land trips tend to be slightly marked up.
One can book land excursions, or just get off and walk the towns, or make separate bookings from home via the net, or just get off and hook up with the plethora of sightseeing hawkers lining the dock...mixed reviews on all methods, and whatever your search/comfort level is.
On both trips, a Princess boat booked excursion that one 'cancels' for any reason, ill/pouring sideways, etc, is not refundable.
In Skagway we rented a beater car and drove up into Yukon territory on Hwy 2 to Caribou Crossing and Emerald Lake: remarkable, empty, spectacular.
Also, in Skagway, we simply lucked into a helicopter tour very late afternoon, to the Mead Glacier: pricey, a 3-4 hr door to door process, but remarkable.
Flickr link of pics from that 13,000 mile 2 month road trip including several of the AK cruise: scroll down about half way on page of pics for AK. There are no crummy 'vacation snapshots' in the mix, I promise.
https://www.flickr.com/photos/452753...7627297418250/
Almost all of the ships hit Glacier Bay/College Fjord: very nice on a sunny day, though we have done an Antarctica 'cruise' and the AK glaciers and 'bergs and scenery pale compared to the South continent.
Many cruise lines offer some combo of a few days on land: usually via bus or train from Whittier or that line's disembarkation port. The bus ride/train ride to Denali Nat Park area is loooonggggg, with an entire day of staring out at trees buzzing by. The Denali area hotels, (usually tied into a specific cruise line), are OK, but make an effort not to be 'moved' from one area hotel to another day after day, which they like to do in the booking, for some reason.
We finally bused back to Anchorage and flew back to V...there are several options depending on cruise line.
As mentioned by wit-nit, the weather can be spectacular to 'when is the rain going to stop' in any summer month, and agree that the state area and topography are so vast that a generalization about weather or temps is a guess.
Casual/outdoor clothes, a rain jacket/hat, sneakers or light boots, bring more money/less clothes.
Also, hit the Cruise sub forum under this Travel forum, use the Search This Forum Tab and plug in Alaska cruise.
Also, do some reading on a Cruise Forum:
Cruise Critic Message Board Forums
And, a forum based on your specific cruise line company, eg Princess:
Princess Cruise Lines - CruiseMates Cruise Community and Forums
Take a few large Gig flash cards, cam batteries/charger, an sense of wonder and interest and have a great time.
My 50Cts...
GL, mD