Celebrated in the month of August / September, Onam is an important festival of Kerala. It celebrates the bounties of nature and a year of good harvest. Ten days of feasting, boat races, song and dance are a part of the festivities.

Kerala's most colourful festival, Onam celebrates the mythical King Mahabali and his golden rule. It welcomes the spirit of King Mahabali, and assures him that his people are happy and wish him well. The story says that gods feared the wise and good rule of Mahabali, the asura (demon) king, thinking that he might become too powerful. They sought the help of Vishnu or the preserver in the Hindu trinity, to curb Mahabali's power. Vishnu took the form of a dwarf called Vamana and approached Mahabali. Pleased with the dwarf brahmin's wisdom, Mahabali granted him a wish. The Vamana asked for three paces of land and the king agreed to it. Vishnu as the dwarf increased his size and with the first step covered the sky, blotting out the stars, and with the second, straddled the nether world. Realising that Vamana's third step will destroy the earth, Mahabali offered his head as the last step. He was pushed to the nether world but as Mahabali was so attached to his kingdom and the loved by his subjects, he was allowed by the gods to return once a year. Onam (Thiruonam) is celebrated on the day when King Mahabali comes from exile to visit his people.

Onam is celebrated as the day of Mahabali return from exile. The festivities begin ten days in advance and floral decorations (Pookkalam) adorn every home. Caparisoned elephants in a spectacular procession, fireworks and the Kathakali dances, are an integral part of the festivities. The Vallamkali (boat race) is one of the main attractions of Onam, and is best seen at Aranmulai and Kottayam. About a hundred oarsmen row huge and graceful odee (boats) with scarlet silk umbrellas. Their number denotes the affluence of the family owning the boat. Gold coins and tassels hang from the umbrellas. Oars dip and flash to the rhythm of drums and cymbals in each boat. In the evening girls perform the Kaikottikkali