You don't need snow to celebrate Christmas. It was Charles Dickens that popularized the whole idea of a "White" Christmas. If we needed snow to celebrate Christmas, most of the US would be out of luck as it usually doesn't snow before Christmas in most of the country. Florida's grandparents would have to stop buying gift for all those ungrateful spoiled grandchildren. New Mexico, Arizona and Texas would be alright since they have a large Mexican population who celebrate the Three Wise Men day on Jan 6th which gives them more presents anyway. Besides, given that Santa's sleigh flies, I'm not sure snow is really necessary. But that red fur coat might have to be exchanged for a cool white robe, and lots of sun block.

In Australia, we celebrate Christmas similarly to other western countries: we invite our family and friends over to our homes, we exchange presents, Christians and Cathiolics read passages of Jesus' birth from the Bible, we eat a traditional roast Turkey and Ham or only eat vegetarian (depending on what branch of Christianity the family practises) etc. Some things we do differently are: going outside (because it's normally warm), have a barbeque, eat seafood and sometimes go to the beach. The only downside of having Christmas in Summer is that in Melbourne (where I'm from) it normally rains on Christmas but last year it didn't, which is good. Also, it's not uncomfortably hot because it's the first month of summer. I hope that answers your question. :)