Sikkim is a very small hilly state in the Eastern Himalayas, extending approximately 114 Kms from north to south and 64Kms from east to west, surrounded by vast stretches of Tibetan Plateau in the North, Chumbi Valley of Tibet and the kingdom of Bhutan in the east, Darjeeling district of West Bengal in the south and the kingdom in Nepal in the west.
The state being a part of inner ranges of the mountains of Himalayaa has no open valley and no plains but caried elevations ranging from 300 to 8583 mtrs above means sea level consisting of lower hill, middle and higher hills, alpine zones and snow bound land, the highest elevation 8583 mtrs. being the top of the Mt. Kangchendzonga itself.
TOTAL AREA STATEMENT
The total geographical area of the state is 7096 sq. Kms. but according to 1958-60 survey operation and the gazatteer fo Sikkim, the land area under different utilization categories is 7299 sq. Kms. Detail break up as follow :
The climate of the state has been roughly divided into the tropical, temperature and alphine zones. For most of the period in a a year, the climate is cold and humid as rainfall occurs in each month. The area experience a heavy rainfall due to its proximity to the Bay of Bengal.
The rainfall in north district is comparatively less than of the other districts. The general trend of decrease in temperature with increase in altitude holds good every where. Pre-monsoon rain occurs in April-May and monsoon (south-west) operates normally from the month of May and continues up to early October.
The mean temperature in the lower altitudinal zone, it varies from 1.5 degree centigrade to 9.5 degree centigrade. Temperature varies with altitude and slope. The maximum temperature is recorded usually during July and August, and minimum during December & January. Fog is a common feature in the entire state from May to September. Biting cold is experienced at high altitude places in the winter months and snowfall is also not uncommon during this period.
An examination of availble rainfall date shows that the mean annual rainfall is minimum at Thangu (82 mm.) and maximum at Gangtok (3494 mm.) . An isohyatal analysis of these data reveals that there are two maximum rainfall areas (i) South-East quadrant, including including Mangan, Singhik, Dikchu, Gangtok, Rongli etc. (ii) South-West corner including Hilley . In between these two regions, there is a low rainfall region e.g. Namchi.
Rainfall in this area is about half of that in the former areas. There is an area in the North-West Sikkim which gets very little rainfall (even less than 4.9 mm.). This area is having mainly snow -covered mountains. Rainfall is heavy and well distributed during the months from May to early October. July is the wettest month in most of the places. The intensity of rainfall during South-West monsoon season decreases from south to North, while the ditribution of winter rainfall is in the opposite order. The highest annual rainfall for the individual station may exceed 5000 mm. and average number of rainy days ( days with rain of 2.5 mm. or more) ranges from 100 at Thangu to 184 at Gangtok.