I will be in shanxi in 20 oct. 2015. I need to know The weather during this time.

Well, it's a big province in China, which contains many cities.
Take Taiyuan (Provincial Capital) as an example, it will be 55 F to 70 F. It may have many sunny days during that period of time. Beside the T-shirts, pants and jeans, it's suggested to bring light jackets in order to adapt large temperature difference.