In case no-one else is able to answer you questions, here are my 'best feeling' answers to your questions.
you can expect any day at sea to have a more formal evening, than the port days. if there is only one day at sea, then look for any half days in port, as they may use this/these for other more formal nights.
The weather over here has been quite miserable for a couple of months now, so definitely pack some wet weather gear. Temperatures around the UK & Europe are only in the 70's wioth no real sign of change in the next month, so The Baltics will probably be a couple of degrees cooler (especially whilst at sea). However any sun you do get, will be bright & strong, so will cause sun burn on unprepared/unprotected skin.
Hope you have a fantastic time,
Alan & Katrinaq
Last: Cunard Queen Victoria January 2016
Next: Oceania Nautica Aug 2016
Then: P&O Oceana December 2016
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