I was just discussing this with a friend, who would win?
The Night King and his army of roughly 100,000 wights and whitewalkers and
*end mild spoiler*
Vs Sauron and his army at the start of LOTR when they fought the last alliance. So this is Sauron with the ring and he has Nazgul on fellbeasts and the Witch King of Angmar.
The Battle takes place on the plains of middle-earth but I am going to say that the Night Ling has brought Winter with him so it is cold.