Climate of Bihar in the south China sea. The maximum frequency of the tropical cyclones in Bihar is during September–November especially during the asterism called hathiya. These cyclones are essential for the maturing of paddy, and are required for the moistening of the soil for the cultivation of rabi crops. Bihar is India's most flood-prone State, with 76% of the population in the north Bihar living under the recurring threat of flood devastation. According to some historical data, 16.5% of the total flood affected area in India is located in Bihar while 22.1% of the flood affected population in India lives in Bihar.
Geography of Bihar which was part of Bihar until 2000 but now is part of a separate state called Jharkhand. Bihar has notified forest area of 6,764.14 km², which is 7.1 per cent of its geographical area. The sub Himalayan foothill of Someshwar and Dun ranges in Champaran district another belt of moist deciduous forests. These also consists of shrub, grass and reeds. Here the rainfall is above 1,600 mm and thus promotes luxuriant Sal forests in the favoured areas. The hot and dry summer gives the deciduous forests. The most important trees are Shorea Robusta (Sal), Shisham, Cedrela Toona, Khair, and Semal.