Having spent Christmas in both summer and winter I don't find either of them strange, but everything about Christmas is more 'believable' one could say if it is not hot and humid outside...
Of course, like posters above have mentioned, in Argentina at least you can go to provinces where it can actually snow and be chilly Dec 25th, but even in Tierra del Fuego they do have a summer, so it's kind of random luck to get that kind of weather (furthermore, in far southern Argentina if I'm not mistaken it is actually not totally dark at midnight!!!)
I think the southern hemisphere gets even in the New Year's holiday. I think it is ways better and tons more fun to celebrate and party in New Year's in warm weather. You can be outside without any worries and dress nicely and comfortably. You can drink, meet girls, set off fireworks, party... I've had much more fun in southern hemisphere new year parties!
[Edited 2003-12-18 17:34:25]
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