Onam is celebrated in the beginning of the month of Chingam, the first month of Malayalam Calendar (Kollavarsham). This corresponds with the month of August-September according to Gregorian Calendar.
Carnival of Onam lasts from four to ten days. First day, Atham and tenth day, Thiruonam are most important of all. Popularity and presentation of rich culture of the state during the carnival made Onam the National Festival of Kerala in 1961. Elaborate feasts, folk songs, elegant dances, energetic games, elephants, boats and flowers all are a part of the dynamic festival called Onam.
Government of India has taken due notice of this vibrant and colorful festival. It promotes Onam internationally in a big way and celebrates 'Tourist Week' for Kerala during Onam celebrations. Thousands of domestic and foreign tourists visit Kerala to be a part of Onam.
Story goes that during the reign of mighty asura (demon) king, Mahabali, Kerala witnessed its golden era. Every body in the state was happy and prosperous and king was highly regarded by his subjects. Apart from all his virtues, Mahabali had one shortcoming. He was egoistic. This weakness in Mahabali's character was utilized by Gods to bring an end to his reign as they felt challenged by Mahabali's growing popularity. However, for all the good deed done by Mahabali, God granted him a boon that he could annually visit his people with whom he was so attached.
It is this visit of Mahabali that is celebrated as Onam every year. People make all efforts to celebrate the festival in a grand way and impress upon their dear King that they are happy and wish him well.
Rich cultural heritage of Kerala comes out in its best form and spirit during the ten day long festival. It is indeed a treat to be a part of the grand carnival. People of Kerala make elaborate preparations to celebrate it in the best possible manner.
The most impressive part of Onam celebration is the grand feast called Onasadya, prepared on Thiruonam. It is a nine course meal consisting of 11 to 13 essential dishes. Onasadya is served on banana leaves and people sit on a mat laid on the floor to have the meal.
Another enchanting feature of Onam is Vallamkali, the Snake Boat Race, held on the river Pampa. It is a colourful sight to watch the decorated boat oared by hundreds of boatmen amidst chanting of songs and cheering by spectators.
There is also a tradition to play games, collectively called Onakalikal, on Onam. Men go in for rigorous sports like Talappanthukali (played with ball), Ambeyyal (Archery), Kutukutu and combats called Kayyankali and Attakalam. Women indulge in cultural activities. They make intricately designed flower mats called, Pookalam in the front courtyard of house to welcome King Mahabali. Kaikotti kali and Thumbi Thullal are two graceful dances performed by women on Onam. Folk performances like Kummatti kali and Pulikali add to the zest of celebrations.