Bhutan consists of three climatic zones – alpine zone, temperate zone, and subtropical zone.
The alpine zone starts at 4,000 metres above sea level. It is characterized by cold climate throughout the year and snowfall for many months. Stunted fir, spruce, juniper, and medicinal herbs grow in the alpine and subalpine regions of Bhutan. Among the many medicinal herbs that grow in the alpine region is highly valued Cordyceps Sinensis. The alpine and subalpine regions of Bhutan are home to nomadic pastures and unique nomadic cultures.
The temperate zone lies between 1,000 metres and 3,000 metres above sea level and includes fertile valleys of Bhutan. It is characterized by moderate climatic conditions with temperatures ranging from 15 to 30 degree Celsius in summer. With most of the zone comprising ancient valley settlements alongside the country’s main rivers, this zone is the cultural heartland of Bhutan. Higher reaches of the zone experiences snowfalls in winter. This climatic zone supports vegetation such as broad-leaved forests at lower elevations and coniferous forests at higher elevations. This zone becomes moist and wet during the monsoon in July and August.
The subtropical zone, which comprises the southern districts of the country, experiences hot and humid conditions with temperatures ranging from 15 to 30 degree Celsius throughout the year. During summer months, temperatures sometimes rise beyond 35 degrees. This climatic zone stretches from 100 metres to 1,800 metres and it is home to broadleaved hardwood and evergreen forests. It has hot summers and warm winters. Owing to thick vegetation, the subtropical region boasts a large variety of animals and plants. This region is home to two distinct ethnic groups called Lhop and Taba Dramtep, ancient communities characterized by cultural and communal practices markedly different from Bhutan’s mainstream culture.
Bhutan’s spring starts in early March and lasts until mid-April. Summer starts in mid-April with occasional showers and continues through the early monsoon rains of late June. The monsoon with heavy rains starts in late June and lasts until late September. Autumn, the most beautiful season in Bhutan, is between late September or early October to late November. Winter, between December and early February, can be very cold in most parts of Bhutan.