In Kerala, Vishu is celebrated as the New Year, as well as the harvest festival, as it marks the day from which the farmers begin the ploughing of land and other agricultural activities.
So what is the origins of Vishu, you may ask.
As per mythology, Vishu is believed to be the day when Lord Krishna killed the demon Narakasura and warded off evil. Another folklore says that Ravana, the demon king, never permitted Surya Deva (the Sun God) to rise from the East, so after Ravana's death, Surya Deva returned and hence, the day is celebrated as Vishu.

Lord Krishna is primarily worshipped by celebrants on the day of Vishu, as he is considered as the God of Time. The festival has been celebrated in Kerala since the reign of Sthanu Ravi Varma aka Kulasekhara, who was the Chera Perumal ruler of Kerala in southern India from 844/45 to 870/71 AD.
Astro Ulagam wishes all Malayalis "Vishu Ashamsakal"!
Source: britannica.com, indiavideo.org
Photo source: India Today, HinduPad, News18 Malayalam