plan to travel to yunyang at chrismas. dec 2012.how the weather.?

It is a bit cold during that time with a low temperature of about 8~12C. You can wear long-sleeved T-shirts or sweater with a coat.

I disagree about the weather in the winter, because indoor heating is rare, you should be prepared to wear an extra layer than just a t-shirt and a jacket, I sometimes have to wear long-johns in the winter, I've been living in CQ for 2.5 years. If you come between November and March, plan on bringing at least a heavy coat (a jacket won't do) and an extra layer maybe even long-johns if you get cold easily