+1^^ on the weather in Ketchikan. I grew up there and recall a few summers where there was less than 12 days when some form of moisture wasn't falling from the sky. It can be very wet.

Coming down from the Yukon, you'll have to hop the ferry at Haines. If you come north then you'll catch it at Prince Rupert.

As digibud described, the country can be sparsely populated with modern conveniences. I'm glad to hear you will have 3 months experience before you get too far North. It is still wild country in a lot of places, even right off the highway.

Good luck. I hope to be in your shoes and engaging that kind of trip within the next 3 years.