Varanasi and Uttar Pradesh
Known as Dev Deepawali
Before dawn, large numbers of devotees bathe in the Ganga at the ghats of Varanasi and offer prayers and lamps. In the evening the long line of ghats along the river is lit with clay lamps, the Ganga aarti is performed on a grand scale, and families float small leaf-cup lamps (deepdaan) on the water. Elsewhere in the state, fairs and holy baths take place at Ganga towns such as Garhmukteshwar and at the confluence in Prayagraj.
Why it matters there: Kashi is traditionally regarded as Shiva's own city, and Dev Deepawali celebrates his victory over Tripurasura with the belief that the gods themselves come to the ghats on this night.
Odisha
Known as Boita Bandana
Before sunrise, people gather at rivers, ponds and the sea to float small boats (boita) made of banana stem, cork or paper, carrying a lamp, betel leaves and flowers. Families sing and call out the traditional refrain remembering the sea voyages of old. In Cuttack the large Bali Jatra fair begins on the banks of the Mahanadi around this day.
Why it matters there: The ritual remembers the Sadhabas, the merchant sailors of ancient Kalinga who traditionally set sail on this season's winds to trade with lands such as Bali, Java and Sumatra, while their families prayed for a safe return.
Rajasthan (Pushkar)
Known as Pushkar Mela
Pilgrims take a holy dip in the Pushkar lake, especially on the full Moon morning, and visit the temple of Brahma, one of very few in India dedicated to him. The famous Pushkar fair, with its livestock and camel trading, folk music and cultural events, is held in the days leading up to the Purnima and reaches its peak on the day itself. Lamps are floated on the lake in the evening.
Why it matters there: Pushkar is traditionally associated with Brahma, and a bath in its lake during the last days of Kartika is regarded as especially sacred.
Bihar (Sonepur)
Known as Sonepur Mela (Harihar Kshetra Mela)
Devotees bathe at the meeting of the Gandak and the Ganga near Sonepur and Hajipur, and worship at the Harihar Nath temple. A large fair, historically famous for its cattle and elephant trading, begins around Kartik Purnima and continues for several weeks.
Why it matters there: The place is linked with the story of Gajendra Moksha, in which Vishnu rescues an elephant held by a crocodile, and with the worship of Vishnu and Shiva together as Harihar.
Punjab and Sikh communities everywhere
Known as Guru Nanak Jayanti (Gurpurab)
Sikhs celebrate the birth anniversary of Guru Nanak Dev Ji, the first Sikh Guru, on Kartik Purnima. Gurdwaras hold a continuous reading of the Guru Granth Sahib (Akhand Path), early-morning processions (Prabhat Pheri), a Nagar Kirtan through the streets, and langar open to all. Gurdwaras and homes are lit up in the evening.
Why it matters there: Gurpurab is a Sikh observance in its own right that happens to fall on the same full Moon; it is celebrated according to Sikh tradition, and people of all backgrounds are welcomed at the langar.
Gujarat (Jain tradition)
Known as Shatrunjaya Yatra
During the four monsoon months (chaturmas) Jain pilgrims traditionally do not climb the sacred Shatrunjaya hill at Palitana. On Kartik Purnima the pilgrimage reopens, and large numbers of devotees climb the steps to the temples at the top, and many also walk the longer circuit (parikrama) around the hill.
Why it matters there: Shatrunjaya is one of the holiest places in Jainism, and the Kartik Purnima yatra marks the joyful end of the chaturmas period of restraint.
Tamil Nadu (a related observance)
Known as Karthigai Deepam
Karthigai Deepam is a festival of lamps observed on the day of the Krittika nakshatra in the Tamil month of Karthigai. Homes are lined with rows of clay lamps, and at Tiruvannamalai a great flame (Maha Deepam) is lit on top of the Arunachala hill.
Why it matters there: It is reckoned by the Tamil solar month and the nakshatra rather than by the lunar Kartika month, so it may fall on Kartik Purnima in some years and on a different day in others.