It's quite early, but I am planning on spending December 2019 in Southeast Asia, dedicating a week to visiting Vietnam. I have never been and would appreciate if someone could point me in the right direction of where to spend my time.

I'm not much of a relax-on-the-beach type of traveler and enjoy something a little bit more active and/or culturally oriented. Hue, Hoi An, and My Son looked really attractive, but I've read that the weather isn't so great in December. I don't mind rain, but would I be better off visiting other parts of the country? Any tips would be greatly appreciated; thanks in advance!