Not sure which is the best month to go, we are booked on a Baltic cruise in July 2008, and looking on the internet the weather looks okay. We did a Med cruise on the Island Escape in June.For the Baltic cruise we are booked a new ship by the carnival line. Carnival Splendor which sails from Dover, I think comencing in June next year.
The weather in the Baltic is a biut unpredictable like the UK. I did a Baltic cruise in july this year and like the UK it was cold, wet and windy most days, That said the summer months should be the best and at least you have the most hours of daylight at this time of yea.
My husband and I were on A cruise to the Baltic in May this year (2007) visiting St. Petersburg (20th/21st) was lovely warm and sunny. But we were told that only a couple of weeks previously it had snowed.
We did the baltic last may/june 06 it was rather like uk had been a month earlier.