I think I got lucky. I had great weather. T shirts and shorts would good for port weather. Wonderful weather in Glacier Bay and College Fjord. Clear, sunny skies.
The outdoor pools are heated as well as the indoors.
I encountered rain showers while in Fairbanks and Trapper Creek. My glacier excursions were about 48 degrees in the clouds.
On the ship I came across other passengers who did a back to back, they said it rained every day for two weeks straight. It is probably not appropriate for me to comment on what others told me.
My suggestion is Realize Alaska has changing weather, and, if you are prepared for anything, you will be extremely pleased when then sun pops out. Bring layered clothing with a breathable raincoat. A backpack in port helps stow lightweight layers as things get warmer.
Please do not let weather deter you from exploring this wonderous, extraordinary place.