The end of September is still fine for Alaska. Near the Glaciers it will be chilly but generally the weather will still be about the same as our September. You must, however be prepared for some rain, Ketchikan gets thirteen feet, yes feet, of rain a year so if you manage to avoid it you're extremely lucky. We have been there in late September and had two or three days of beautiful weather and three days of rain and mist, the rest being ok. As you will be going at the end of the season be prepared for some brilliant marked-down prices on goods particularly windcheaters etc. we loved every minute of it and indeed had, they said, one of the best whale watching trips of the season......make every moment count....Nei.
I;ve been their september and weather was drizzle but mild.I would suggest a balcony cabin if you can because the scenery is awsome especially glacier bay. a small umbrella will be handy and whale watching is a must.Coming from Aberdeen will feel like summer.
It rained on us in Ketchikan as well! I found it quite chilly at times and a windcheater is a must. Yes, a compact umbrella is a good idea.
It was blowing a blizzard at the Hubbard glacier and pretty cold but the staff are on hand with pea and ham soup and hot chocolate drinks,saw some whales,got great shots of the glacier it was cold but superb,Enjoy it ,take a warm jumper and a good all weather coa.