ONAM FESTIVAL...

The harvest festival Onam (ഓണം) is the major festival celebrated in Kerala, India. It is also the State festival of Kerala.

The festival falls during the Malayalam month of Chingam which is the first month according to the Malayalam calendar (Aug - Sep) and marks the commemoration of home-coming of the King Mahabali In Kerala, it is the festival celebrated with most number of cultural elements such as Vallam kali, Pulikali, Pookkalam, Onathappan, Tug of War, Thumbi Thullal, Kummati kali, Onathallu, Onavillu, Kazhchakkula, Onapottan, Atthachamayam etc. Onam is reminiscent of Kerala's agrarian past, as it is considered to be a harvest festival.
Onam is an ancient festival which still survives in modern times. It is one of the rarest festivals which is celebrated by a complete State, irrespective of religion, caste and creed. Kerala's rice harvest festival and the Festival of Rain Flowers, which fall in the month of Chingam.

The celebrations begin within a fortnight of the Malayalam New Year and go on for ten days. All over the state of Kerala, festive rituals, traditional cuisine, dance and music mark this harvest festival. The ten-day Onam festival is considered to be flagged off with Atthachamayam (Royal Parade on Atham Day) inThripunithara (a suburb of kochi City). The parade is colourful and depicts all the elements of Kerala culture with more than 50 floats and 100 tableaux. The main centre of festival is at Vamanamoorthy Thrikkakara temple, within Kochi City, believed to be the ancient capital of King Mahabali. The temple is dedicated to Lord Vamana and is directly linked to the mythological background of Onam.

The ten days of Onam are celebrated with great fanfare, by Malayalees. Of all these days, most important ones are the first day, Atham, and the tenth and final day, Thiru-Onam (Thiruvonam). The rich cultural heritage of Kerala comes out in its best form and spirit during the festival.

https://en.wikipedia.org/wiki/Onam