I sailed with Oriana on the Baltic Cruise from 6th July to 20th. The weather for the first 3 days was rather wet, but not cold. Each day after that it improved and the 2nd week was warm and sunny. The hightlight was St. Petersburg, but every port was interesting. Don't expect a relaxing crusie, as there aren't many days at sea, and going on this cruise and not visit the places would be a waste. It's a cruise I've wanted to do for many years, and thoroughly enjoyed, but would not do again as I like the med. for the weather and more sea days.
I would recommend it, but not be too disappointed if weather not too good.