What about December? Is it okay to visit in China? Is it Winter season?

You are recommended to visit the southern regions of CN in December, such as Guangzhou, Guilin, Yunnan, Hong Kong, and Macau, for the weather is not very cold during that time in those cities. If you want to visit the central and northern regions, it may not be an appropriate time, for it can be very cold in these areas. You may change the schedule to March, April, May, September, or October. It is very comfortable to set out a tour during this period.