What to wear in Beijing and Sichuan in Dec 7-20?

It is really cold during that time in Beijing. The average low temperature may be about -10℃. You will have great chance to see snow and ice there. Better wear down jackets and boots. Since it may have strong wind and the road may freezes, you need to prepare windproof coat and antiskid shoes.
The usual temperature in Sichuan at that time may be about 0~5C.It is cold, warm clothing is a must. Jiuzhaigou may be colder, need warmer clothes when go there. While climb the mountain, antiskid shoes is better choice.
Well. China Weather(https://www.travelchinaguide.com/climate/) provides a lot information about weathers in these cities. It is helpful to us.

Hi,Ms Mae. I would like to give you some advice. Two-week time is enough for you to visit both Beijing and Sichuan. When attending the conference in Beijing, you can make time to visit the Great Wall which is a must sightseeing. In your spare time, you can go to the forbidden City, Tian'anmen Square and Summer Palace. Many beautiful Beijing attractions are waiting for you.
After the conference, you can fly to Sichuan.Jiuzhaigou Scenic Area, Huang Long Valley and Mt. Emeishan, you should not miss these attractions.
Well, go to look the Best China Tours(https://www.travelchinaguide.com/tour/best-china-tours.htm) , you could make full use of your time and enjoy yourself in China. China Tour(https://www.travelchinaguide.com/tour/default.htm) is also a good reference.