I am going to Meixian and GuangXi in first week of Dec. and like to know is the weather ?

I wonder if you refer to the Meixian County of Guangdong. If so, it will be cool even a little cold during that time. Based on the weather records of the past years, the lowest temp may fall to 6-8C/43-46F and the hightest can be around 25C/77F. Sunny days would be the majority, good for travel. I suggest you prepare jacket, jeans, long-sleeved shirts/cardigans and light sweaters.

Guangxi area would be a little cooler than Meixian. The temp range may be 6C/43F - 20C/68F. It will have many cloudy days as well as some lightly rainy days. Together with the garments above, leather jackets and long johns are necessary.