The importance of Atham is that this is held 10 days before the most important Onam event -- the 'Thiru Onam', which this year falls on September 11.
According to legend, it was during the reign of King Mahabali that the King's annual visit to see his subjects happened and this visit has since been celebrated as Onam.
Last year, due to the worst ever floods to hit the state in a century, there were no Onam celebrations and this year too the flood-affected parts of the state are celebrating the festival in a muted manner. The Kerala government had last month announced that this time the Onam celebrations would be held in a low key manner.
Over the years, Onam has become the one festival which is celebrated by all the sections of Kerala society.
Onam falls in the month of "Chingam" which is the first month according to the Malayalam calendar.
Incidentally, in the bygone era when untouchability prevailed in the state, this was one event which was open to all the citizens. Thousands of people, including foreign tourists, witness the colourful and popular cultural extravaganza.
Starting from Monday the one thing that cannot be missed are the 'pookalam'-- the floral carpets made out of fresh flowers on the ground -- outside the homes and offices and almost all places in the state. These flower decorations are the visual expressions of happiness and are extremely popular with people of the state.