The princely Kingdom of Bhutan is a landlocked country, about 300 km long and 150 km wide encompassing an area of 46,500 square kilometers. Located between longitude 88045′ and 92010′ East and latitudes 26040′ and 28015′ North in the Eastern Himalayas, it is bounded by India in South and South-West and Tibetan autonomous region of China in the North and North-West respectively.
Virtually the entire country is mountainous, and ranges in elevation from 100m along the Indian border to the 7,554m Kulha Gangri peak on the Tibetan border. These two extremes frame a landscape which stretches from sub-tropical to arctic like conditions. The maximum East-West stretch of the country is approximately 300 km and north-South about 150 km.
Talking in geomorphologic terms, Bhutan is distinctively divisible into three lateral zones from South to North. Incidentally, this zonation is more or less applicable to meteorological, ethnographical and geographical divisions of the country.
The Great Himalaya
Extending from Mt. Chomolhari (7,314m) in the West to Kulha Gangri (7,554m) near the center point of the northern border between Tibet and Bhutan, this region is virtually a snow-wilderness zone where almost 20% of the land is under perpetual snow. This zone is represented by alpine meadows and perpetually snow bound high summit of the Great Himalayan range.
The Inner Himalaya
This is the largest physiographic region of Bhutan and lies among broad valleys and forested hillsides from 1,100m to 3,000m in elevation. All the major towns of Bhutan are situated in this zone such as Paro, Thimphu, Punakha, in western Bhutan, Trongsa and Bumthang in central Bhutan and Mongar, Trashigang in eastern Bhutan.
The Southern foothills
Also called as Himalayan foothills, this zone occupies the southern most part of the country. The plains in the south of the country are part of the region known as Terai, which extends from Kashmir, through Nepal, to Bhutan. The average annual rainfall in this region generally reaches up to 200 inches resulting to luxuriant vegetation particularly tropical forests rich in wildlife, while at times hot, steamy and unhealthy tracts are other features of this zone.
Rivers play an important role in Bhutan’s physical, economic, social and cultural geography. Their enormous potential for hydroelectric power has helped in shaping the national economy. Since the central Himalayas of Bhutan receives the full brunt of the monsoon so the rivers are larger and have created much broader valleys than rivers further to the west in Nepal and India. In their upper reaches, most Bhutanese rivers have created large fertile valleys such as those of Paro, Punakha, Thimphu and Bumthang. As the rivers pass through the centre of Bhutan, the valleys become steeper and narrower, and roads have to climb high on the hillside. The principal rivers of the country are; Am-mo-chhu, Paro Chhu, Wang Chhu, Puna-Tsang Chhu, Mangde Chhu, Pho Chhu, Mo Chhu, Dangme Chhu, Manas Chhu and Changkhar Chhu.
Bhutan’s climate varies widely depending upon elevation. In the southern region it is tropical, with a monsoon season and eastern part is warmer than the west. The central valleys of Punakha, Wangduephodrang, Mongar, Trashigang and Lhuntshi enjoy a semi-tropical climate with cool winters, whereas Paro, Thimphu, Trongsa and Bumthang have relatively harsher climate including snowfall in winter.
In the valleys where most tourist activities are concentrated, the winters (mid-November to mid-March) are dry with daytime temperatures of 16 – 18 degree centigrade while evening and early morning are cold with night time temperature sometimes falling below zero.
Spring lasts from mid-March to the beginning of June, with temperatures warming gradually to 27 – 29 degree centigrade by day and about 18 degree centigrade at night. However, cold spells are possible up until the end of April, with a chance of new snow on the mountains above the valleys. Strong, gusty winds start blowing almost every day from noon to early evening . The first storms break, and they become more and more frequent with the approach of the monsoon which arrives in mid-June.
The country receives abundant rain especially in the south, as it gets full face of monsoon coming from the Bay of Bengal. To which its mountains form a barrier. At the end of September, after the last of the big rains, autumn suddenly arrives and sky gets clear, a brisk breeze picks up and temperature starts falling towards freezing at night although bright sunshine continues to keep the days warm. Autumn is the magnificent season that lasts until mid-November and it is the best time to visit this fascinating mountain Kingdom.