just a general word on airconditioning - I have become more accustomed now to the American habit of air conditioning, and find DLRP stuffy even in winter. The attraction queues get quite hot, or in the case of Pirates steamy. In winter I often wear just a t-shirt or polo shirt covered by a wool peacoat.
Shops and restaurants in Europe also may not be air conditioned. Paris is a little better than much of Germany, last summer we were there during World Cup and a friend of mine gave up and went to Paris after a few days due to the lack of cool air in Bavaria. On the train don't expect to open a window unless you ask permission first - many Germans are still worried about getting a draft.