I have been here for the winter and it has been pretty cold. July for a couple of weeks was really cold but donīt let that put you off. All in all, Argentina is a fantastic country to visit any time of the year. My highlights so far are:
Cordoba - a beautiful, friendly, relaxing city with a nice vibe
Iguazu Falls - stunning, stunning, natural wonder - you have to go!
Buenos Aires - Fantastic city (I had a great time studying at
http://www.viaspanish.com)To answer your question - Argentina is great any time of the year