Even Michael Fish cannot predict the weather - so we are totally unable to. I did this cruise in July this year and it was freezing, my friend did it in August and it was freezing, and my mum did it in May last year and it was a heatwave. Go figure.
If you think of the weather you would expect in England in a normal summer then allow for a difference of 10'F/15'F up or down on that you will probably arrive a a reasonable conclusion. The current weather is so unpredictable I have never known, in all my 105 years experience, anything to equal it so let's hope it reverts to something more normal soon. ... Neil.
When we were in St Petersburg in July it was 80 degrees, but apparently that's rare. The guide told us they get the first ground frosts in August. Take clothing you can layer and something waterproof - it rains a lot. It is a very interesting trip with something to see every day. I hope you are lucky with the weather and have a great holiday.
We were in St Petersburg 11/12 September this year and the temperature, according to the ship's log, was 12C. I wouldn't exactly say it was freezing, but a chill wind made it feel much cooler. The highest temperature was 18C in Copenhagan and the lowest 9C in Tallinn. Other ports of call, Stockholm, Helsinki, Gdynia and Oslo ranged between 12C - 17C. Who knows, though, it could be completely different next year. As Cooke advises, take layers and waterproofs. St Petersburg is amazing!!