Onam is a holiday with Hindu roots that pretty much has become a harvest festival. Prosperity seems to be the theme. Today, there's no religious lines regarding Onam, and it is enjoyed by everyone throughout the state of Kerela. It goes on for 10 days or so, and stores shut down rather randomly throughout those 10 days. So, stock up.
Near our flat is the hub for festivities in our city. Cora braved some amusement park rides. If the spinning doesn't get you noxious, the gas (we say petrol here) fumes will.