What is the weather like on the Danube in the early part of October. Also suggestions on how to dress while visiting Bulgaria, Serbia, Germany, Austria, Hungary and Slovakia in early October.

weather is ok for cruises in that time, still ok fo rbike riding when off the ship etc.. As for clothing in those areas layers and layers and a light jacket with a warm scarf was what I used in that time in Austria and Slovenia. Only used the jacket when in the mountains in Austria and when raining.

The weather is not that bad in early October, it is becomming cold in the first half of November, although now it is not as used to be weather may change from one day to another, before it was happening gradually but it looks like 2 out of 4 seasons are disappearing....however, you should be fine with some light jacket.