We were there first part of June. Weather was great in Ketchikan and first day at sea, cool and cloudy the rest of the time. Our neighbors went last week. They said it was mostly overcast and sprinkled lightly. Weather averaged between 60 and 70 during the day.
As for ship information, what one are you one? We were on the Sun and thought it was great.
It was the hottest day on record in Juneau the day we were there (21st June, longest day!), and we were blessed with sunny and hot/warm weather for the whole week. We sailed on the 'Oosterdam', but saw the 'Radiance of the Seas' and she also looks like a beautiful vessel. Have a great time, I'm sure you will enjoy it whatever the weather.
Some photos of our trip at http://www.bondpix.com/Alaska_Cruise.htm