If it is hill stations in Tamil nadu, then my suggestion would be ooty. Ooty is Heaven on Earth. I went to ooty last year , 2009 august. the climatic condition in ooty was awesome. We've got lots and lots of places to visit there. The monkey falls, the Dhyanalinga falls( called the aindhu aruvi in tamil), the Maasaani amman temple, the Botanical gardens, boat house, the ninth mile shooting spot, dodda beta and many more places to visit.on the way to ooty, there is a theme park at mettupalayam, Black Thunder. It is ultimate fun being there.
The Nilgiris is also famous for its eucalyptus oil which cures multitude of ills in humans, the tea powder from the famous tea estates of nilgiris and last but not the laest , the home-made chocolates.we can get different varieties of fresh fruits in Nilgiris . so.. friends .. if you are planning for a summer vacation, ooty is the best Hill station in TAMILNADU.