The thumb-shaped state of Sikkim is characterised by wholly mountainous terrain. Almost the entire state is hilly, with the elevation ranging from 280 metres (920 feet) to 8,585 metres (28,000 feet). The summit of the Kanchenjunga is the highest point. For the most part, the land is unfit for agriculture because of the precipitous and rocky slopes. However, certain hill slopes have been converted into farm lands using terrace farming techniques and is used for cultivation. Numerous snow-fed streams in Sikkim have carved out river valleys in the west and south of the state. These streams combine into the Teesta and its tributary, the Rangeet. The Teesta, described as the "lifeline of Sikkim", flows through the state from north to south. About a third of the land is heavily forested.

The Himalayan mountain range in North Sikkim.The lofty Himalayan ranges surround the northern, eastern and western borders of Sikkim in a crescent. The populated areas lie in the southern reaches of the state, in the Lower Himalayas. The state has twenty-eight mountain peaks, twenty-one glaciers, 227 high altitude lakes, including the Tsongmo Lake, Gurudongmar and Khecheopalri Lakes, five hot springs, and over 100 rivers and streams. Eight mountain passes connect the state to Tibet, Bhutan and Nepal.

CLIMATE
The climate ranges from sub-tropical in the south to tundra in the northern parts. Most of the inhabited regions of Sikkim, however, enjoy a temperate climate, with the temperatures seldom exceeding 28 °C (82 °F) in summer or dropping below 0 °C (32 °F) in winter. The state enjoys five seasons: winter, summer, spring, and autumn, and a monsoon season between June and September. The average annual temperature for most of Sikkim is around 18 °C (64 °F). Sikkim is one of the few states in India to receive regular snowfall. The snow line is around 6,000 metres (19,600 feet).

During the monsoon months, the state is lashed by heavy rains that increase the number of landslides. The state record for the longest period of non-stop rain is eleven days. In the northern region, because of high altitude, temperatures drop below -40 °C in winter. Fog also affects many parts of the state during winter and the monsoons, making transportation extremely perilous.