Hi, it would be cold but I think you'll get another view of Xian in Autumn, maybe you can see snow here at that time! To me, Xian in winter has another charm. For tours, you can check the Xian Tour Packages(https://www.travelchinaguide.com/package/xian.htm) webpage on this website, there are several standard of tours you can choose also the standard of hotels. The room standard will be in terms of the hotel's rate, such as budget to luxury facilities. In cold winter, these hotels do equipped with good heating-system. Wish you have a good time!