scale ranging from in order of increasing susceptibility to earthquakes, the state lies in seismic zone V. Climate The state has a tropical savanna climate, designated Aw under the Köppen climate classification. The undulating topography leads to local variations, particularly in the hill ranges. The four main seasons are winter, from December to February; pre-monsoon or summer, from March to April; monsoon, from May to September; and post-monsoon, from October to November. During the monsoon season, the south west monsoon brings heavy rains, which cause frequent floods. The average annual rainfall between 1995 and 2006 ranged from . During winter, temperatures range from , while in the summer they fall between . According to a United Nations Development Programme report, the state lies in "very high damage risk" zone from wind and cyclones. Flora and fauna Like most of the Indian subcontinent, Tripura lies within the Indomalayan realm. According to the Biogeographic classification of India, the state is in the "North-East" biogeographic zone. In 2011 forests covered 57.73% of the state. Tripura hosts three different types of ecosystems: mountain, forest and freshwater. The evergreen forests on the hill slopes and the sandy river banks are dominated by species such as Dipterocarpus, Artocarpus, Amoora, Elaeocarpus, Syzygium and Eugenia. Two types of moist deciduous forests comprise the majority of the vegetation: moist deciduous mixed forest and Sal (Shorea robusta)-predominant forest. The interspersion of bamboo and cane forests with deciduous and evergreen flora is a peculiarity of Tripura's vegetation. Grasslands and swamps are also present, particularly in the plains. Herbaceous plants, shrubs, and trees such as Albizia, Barringtonia, Lagerstroemia and Macaranga flourish in the swamps of Tripura. Shrubs and grasses include Schumannianthus dichotoma (shitalpati), Phragmites and Saccharum (sugarcane). According to a survey in 1989–90, Tripura hosts 90 land mammal species from 65 genera and 10 orders, including such species as elephant (Elephas maximus), bear (Melursus ursinus), binturong (Arctictis binturong), wild dog (Cuon alpinus), porcupine (Artherurus assamensis), barking deer (Muntiacus muntjak), sambar (Cervus unicolor), wild boar (Sus scrofa), gaur (Bos gaurus), leopard (Panthera pardus), clouded leopard (Neofelis nebulosa), and many species of small cats and primates. Out of 15 free ranging primates of India, seven are found in Tripura; this is the highest number of primate species found in any Indian state. The wild buffalo (Bubalus arnee) is extinct now. There are nearly 300 species of birds in the state. Wildlife sanctuaries of the