If you are planning any kind of glacier hike, then the warmer jacket may be needed. Sometimes, they will profide the real warm jackets, otherwise just layer like the previous poster suggested. Pack some t-shirts and sweat shirts and you should be fine. Don't forget some kind of rain gear as well.
what kind of jacket/coat should I bring? I am cruising Alaska 7/4-11, and need to know if a spring coat will do, or a winter jacket?
1. In Ketchikan and Juneau, and along the associated segment of the inside passage, you are likely to encounter temperatures in the upper 50's to middle 60's F (middle to upper teens C) and rain, so you'll need a waterproof windbreaker or spring/fall jacket.
2. Calving of glaciers provides a steady supply of ice into the bays where they meet the ocean, ensuring that those bays remain full of ice water, which has a temperature of 32 F (0 C), and the air above them is not much warmer. While viewing glaciers, you will want a winter jacket, hat, and gloves. The same is true of any shore excursion in which you fly in a helicopter that lands on a glacier.
3. In Anchorage and Fairbanks, clear weather and temperatures in the 80's are common.