book train from Shanghai to Xi'an

1. The first week of november the temperature in Danxia how much degree in celcius? Is it under 0 deg celcius? It is important for my preparation.
2. If I depart from Shanghai first November, when can I book the train at earliest day. I mean can I book 10 days before, or 15 days before
3. Kindly advice me, what is the good/ popular website to book it

Thank you
Best regard
Sri mujiati