Define "warmish." If by that you mean short-sleeve weather, then no. Will you get snow and ice? No. Typical Alaskan weather during that time--heck, during most of the Alaskan summer--means 50s and 60s with a fair amount of overcast skies, drizzle, and lows perhaps in the 40s. That's the typical weather, but your particular experience might be different, but I wouldn't count on it. That being said, Alaska is a majestic place to visit, and as long as you dress appropriately (layers, water-resistant outer jacket, et. al.), you'll have a great time.I was looking at Sep 2 Alaska sailing..is this too late to go and hope for warmish weather?
We went on the next to last cruise of the season (so September), and it was in the 50s. We thought it was fabulous! (a cool break for us after a long hot summer) Plus, at the end of the season, everything in the ports is on sale! (fleeces, sweatshirts, etc)
We were on the last Alaska cruise in 2011 (Aug 29 - Sep 7) and had similar weather - temps in the hi 50's - low 60's. It was misty/sprinkly in Juneau, but otherwise clear, from what I recall. Bring a waterproof outer layer and waterproof/resistant shoes, a hat & gloves and you should be fine.
We were on the August 27 - September 3, 2012, cruise and had beautiful weather the entire week. Every port we were going around in T-shirts and sunglasses! Temps were in the mid to upper 60's. Glacier day was gorgeous. So, warm temps in early September are possible!
Our first cruise to Alaska was 18 Sep 2009 (not DCL). The weather was actually quite similar to what we had on our last Alaska cruise in June 2012. Generally about 50-55 degrees daily. Glacier Bay day & Juneau (both times) overcast and drizzly. The biggest difference was the amount of daylight. In June sunrise was around 4:30 am with sunset around 10:30pm. In September sunrise was around 7:00am with sunset being around 8:00pm.