It is observed to celebrate the harvesting of grain. It is usually held on the 14th and 15th of January (1st and 2nd Maagh, the tenth month of Assamese calendar). The first day is called Uruka, when people build a temporary shed and have feast. Four bamboo rods are placed beside the four posts and then a meji (a pile or column on split fire-wood or straw erected for burning in the early morning of the Maagh Bihu) is built in the shape of a temple, in a conical shape. In the early hours of the next day people take a bath and after the meji is lighted, they pay their respect and the Bihu is officially started. The ashes of the burnt meji is scattered over the fields, for it is believed that doing so would increase the fertility of the soil. Delicacies like pithas are served together with Jalpaan. Various kinds of potatoes (Kaath Aloo, Mitha Aloo etc.) are also eaten on this day. Many games are also played keeping the spirit of the Bihu alive. Bihu is the treasure of the Assamese, something which they have to protect at all cost. But now commercialisation has cost Bihu some of its lustre. In place of Chira, pithas, curd, cakes, biscuits etc. have taken over. Bihu dances and songs have been restricted to the stage with its being brought within the bounds of competition.
Among the tea tribes of Assam, there are many festivals which are very popular, among which mention may be made of Karam Puja and Tusu Puja. Karam is celebrated on the 5th day of Bhadon month. It has celebrated in two types — Rajah Karam and Jitiya Karam. For Jitiya Karam there is no such hard and fast rule. There are many types of songs, which are sung on the occasion of Karam Puja like Bandana, Khemta, Dat, Jhumur, Rang and Bhincheria songs, Tusu Puja is celebrated in the month of Puh and Maagh (Makar Sankranti).