December is a month of winter in China. Most places are cold. Especially, the Northeast and Northwest are much colder. However, the winter of the Northeast is very beautiful. Take Harbin for example. It's a city in Heilongjiang Province, the northeast of China. You will see much snow and go to visit the ski resort. However, if you don't like cold places, you may go to Haikou, Sanya or Kunming in the South China. These cities would be warmer than the north. Ps: Actually, the winter of North China is not so hard. Although it's cold outside, it's still very warm when you are in the hotel, as the hotels always provide air conditioners or heaters. BTW, I am from Xian. Welcome to Xian City!