Why people of south india use sour so much in their daily food?

it may add the taste to their food.. it might be their tradition to do so..

I don't know if it has any link with weather. Each region has a typical aspect to it's cooking. Karnataka cooking uses a bit of sweet in it's spicy dishes like sambar. Andhra cooking is all about making food delightfully spicy. Kerala cooking uses coconut oil to add that very different flavor. Gujrathi cooking is all sweet-sweet. Panjabi cooking is all about richeness, too much paneer and oil.

I am from chennai and i have lived there all my life. One thing i found out after coming to india is that people in south india just like a variety of tastes and much spice in their food. it is not only sour but a variety..thats what i means, i dont think it has got to do anything with the climate though

A wide variety of ppl in south india like different tastes of food. Especially those like the dosas and idlies. Im a west indian ( Gujarat !) hehe :P

Hi, I think you haven't tasted the typical home made lunch in chennai. It is a balanced mix of sweet (payasam-sweet porridge), spicy (sambar and rasam-to be mixed with boiled rice), sour (vatthakuzhambu and curd-to be mixed with boiled rice), snacks (papad or vathal-fried in oil) and hot (pickle) stuff guaranteed to satisfy your taste buds. In addition, it consists of curry and kootu (made from vegetables). Tamilians have described six types of culinary tastes in their literature. After a hearty meal like one above, consume a banana and chew betel nut packed inside betel nut leaves sprinkled with calcium carbonate. Go sit in a chair for the next 30 minutes and experience heaven.