The festival, marking the transition of the Sun from the Dhanu (Sagittarius) sign to the Makara (Capricorn) constellation, signals the start of the summer solstice, with days gradually getting longer and warmer.
After the traditional morning pooja ceremonies, Mumbaikars exchanged 'til-gul' (ladoos made with sesame, jaggery and oil/ghee) and wished "Til-gul ghya, Ani godd-godd bola" (Eat til-gul, Speak sweetly).
The huge Tamilian community in central Mumbai and other parts of the city celebrated the day as Pongal or the joyous harvest festival.
Over 2,000 housewives from Dharavi gathered before sunrise on the long 90-feet main road and cooked kheer of rice-and-milk on an open fire in a metal pot, tied a turmeric plant around it and then offered it to the Sun God along with other oblations.
In Tamil Nadu, Pongal is largely a rural festival, and spread over the four days of the harvesting season, said Matunga resident and social worker K. A. Viswanathan.
Elsewhere, lakhs of Mumbaikars of all ages trooped out in the open, on rooftops, terraces, trees and higher places flying millions of colour kites of all shapes and sizes, indulging in friendly 'kite-fights' and running to grab the felled ones of the opponents.
Many restaurants and hotels are offering a daylong special Makar Sankranti menu with decorative kites and 'manja' strings, tiny kites with the cocktail stirrers and other attractions for the festive season.
Mumbai's glamour and film industry also celebrated the fest in a big way with photos and messages on social media and television channels, greeting their fraternity and the masses.
Makar Sankranti is celebrated all over India with different names like Lohri, Bhogi, Pongal, Magar Jyoti, Bhogali Bihu, Sankrant, among others, and generally falls on January 14/15.
The day signifies the movement of the Sun from the inauspicious Dakshinayana (southern hemisphere) to the auspicious Uttarayana (northern hemisphere), Viswanathan said.
In Hindu mythology, it was on this day that Lord Vishnu ended the ever-increasing terror of the Asuras (demons) by finishing them off and burying their heads under the Mandar Parvat.
Hence this occasion also identifies a period of enlightenment, peace, prosperity, happiness, spiritual cleansing, among others.
( With inputs from IANS )