The story
Ambubachi Mela in Guwahati
Kamakhya Temple in Guwahati closes for three days each Ashadha when tradition holds the goddess Kamakhya menstruates, timed to the sun's entry into Mithuna on the Assamese calendar. The sanctum's yoni-shaped stone is covered, then bathed and reopened on the fourth day, drawing Aghoris, Naga sadhus, and tantric practitioners from across India in what is widely called the largest tantric gathering in the country.
When the monsoon reaches Assam and the Brahmaputra begins running red with iron-rich silt, priests at Kamakhya Temple on Nilachal hill close the sanctum for three days during the Assamese month of Ahaar, timed to the sun's entry into Mithuna.