We were told it rains in Ketchikan more than 300 days a year, and over 150 inches. We were there last month and it was a light rain throughout most of the day. At times the rain may get heavier, but for the most time it is a light rain. Alot of light rain. It is like a tropical rain forest in Alaska.
Juneau was also a light rain, with periods of sun. Skagway had a great day, sun, temp. of 82 F, but that is not the usual. It can be overcast and very cold there.
We wore a combo rain jacket and warm jacket, like you might use when boating. Waterproof, but warm. We carried small unmbrellas that I never used but my wife did. I always wore a had to keep the mist off of my glasses as well.
The weather puts a gloom on photographs. Colors are mutted and not as sharp as with sunshine.
Plan on the rain and hope for the sunshine to come out.