Sikkim, the second smallest state of India having an area of around 7096 sq. km is known as the paradise of naturalists. It is a thumb shaped hilly region with Nepal in the west, Bhutan in the east and Tibet in the north and north-east. In the south it is bordered by Darjeeling district of West Bengal. The mountain chains which run southward from the main Himalayan ranges form the natural border of Sikkim; the Chola Range dividing it from Tibet in the north east and Bhutan in the south-east; the Singalila range likewise separating it from Nepal in the west. Mountain passes along these ranges over the years have sustained a two way traffic of traders, pilgrims, and adventurers from Tibet and Central Asia. The most well-known of these passes are Nathu La (4392m), Jelep La (4388m), Donkia La (5520m), and Kongra La (4809m). The topography of Sikkim is quite varied. The elevation ranges from ca 300 to 8586 m. Mt. Khangchendzonga (8586 m) – the third highest mountain of the world- lies on the border with Nepal. Teesta and Rangit are two main rivers which flow in a north to south direction through gorges and valleys.
Sikkim provides a great variety of habitats that support and sustains rich flora and fauna. The vegetation changes from tropical to subtropical upwards through middle hills with much coniferous and oak forests of temperate character to the higher slopes with sub alpine scrub and alpine “meadows” generally related to higher alpine flora of the North Temperate Zone.
Sikkim has been known to be the most humid region in the whole range of Himalaya, because of its proximity to the Bay of Bengal and direct exposure to the south-west monsoon. The annual rainfall ranges from 200 – 500 cm in most of its inner valleys except for its northern most region which receives scanty rainfall. Throughout the year, but particularly from June to September, monsoon brings heavy rainfall to the state. Lower hills and valleys enjoy a sub-tropical climate, warm in winter, hot and extremely humid in summer. Towards interior the climate becomes gradually more temperate with cool winters and hot summers and often heavy rainfall. In northern part of the state the summers are short and cool, and winters with considerable snowfall and frost