Bhutan is a landlocked country, about 300 km long and 150 km wide, encompassing an area of 46,500 square kilometers. Located between longitude 88 45 and 92 10 E, latitude 26 45' and 28 15' N in the Eastern Himalayas. It is sandwiched between India from the South and Southwest and Tibetan Autonomous Region of China from the North and Northwest.
Virtually the entire country is mountainous, rising like a giant staircase, starting from 100 meters along the Indian border to the 7,500 meters to the northern border with Tibetan. Within this frame of landscape stretches sub-tropical to arctic vegetation and climatic conditions. As such, the land can be defined in three distinct zones.
Extending from Mt. Chomolhari (7,314m) in the West to Mt. Kulha Gangri (7,554m) close to the midpoint of the northern border, this is region of alpine wilderness where 20% of the land is under perpetual snow. The zone is typically alpine meadows surrounded by perpetual snow bound peaks of the Great Himalayan range.
This is the largest geographic zone ranging from 1,000 meters to 3,000 meters within which lie the broad fertile valleys and rich hills. All the major settlements of Bhutan including Paro, Thimphu and Punakha in the west, Trongsa and Bumthang in the central and, Mongar and Trashigang in the east lie in this zone.
This zone of Himalayan foothill occupies most of the southern part of the country. The southern plains are part of Terai region, which extends from Kashmir, through Nepal, to Bhutan. The average annual rainfall in some parts of this region can reach as much as 200 inches resulting in luxuriant tropical and sub-tropical vegetation rich in flora and fauna.
Due to the high snowcapped mountains and snowfields complemented by numerous valleys, Bhutan is blessed with abundant rivers. Also, the south face of the mountain barriers stop moisture-laden air traveling from the Bay of Bengal causing monsoon, the rainy season. Most fertile valleys in the country are as the result of the rivers and in modern days the rivers have proved to be great resource for generation of hydroelectricity.
The principal rivers of the country are Am-mo Chhu, Paro Chhu, Wang Chhu, Pho Chhu, Mo Chhu, Puna-Tsang Chhu, Mangde Chhu, Chamkhar Chhu, Dangme Chhu and Manas Chhu.
Climate varies widely depending upon elevation. The southern region has tropical climate, very hot in summer and warm in winter and gets the brunt of monsoon season. The central valleys of Punakha, Wangdue, Mongar, Trashigang and Lhuntshe have semi-tropical climate with hot summers and cool winters. The higher valleys of Paro, Thimphu, Trongsa and Bumthang have relatively harsher climate including snowfall in winter while summers are not too hot.
In the valleys where most tourist activities are concentrated, the winters, from mid-November to mid-March, are dry with daytime temperature ranging from 14 - 18 degrees centigrade while evening and early morning tend to be cold and night temperature often fall below zero degrees.
Spring lasts from mid-March to the end of May, characterized
by day temperatures in early 20 degrees centigrade and high as 18 degrees centigrade
at night. Occasional cold spells brew until the end of April, with chance of
fresh snow on the mountains surrounding the valleys. One common characteristic
for both winter and spring is the afternoon wind, which starts after 2 p.m.
lasting for couple of hours.
As it becomes warmer in summer the monsoon rain moves in. It starts in July
and ends towards late September. The height of monsoon is mid-July to mid-August.
Although the whole country gets its share, the southern regions receive the
heaviest of the rain.
By mid-September, after the last of the big rains, autumn arrives and sky can be spotlessly clear most days. It lasts till mid-November. The climate is no different from late spring until afternoon wind starts to pick up and winter comes around once again.