The Hindu Kush-Himalayan region - Climate (2/3)
In the subtropical mountains along the Himalayan ranges the rainfall increases from west to east and from the inner to the outer parts of the ranges. At the sub-alpine and alpine levels, rainfall ranges from less than 1,000 to 1,500 mm per year with at least one or two dry months even up to seven or eight. The mean temperature of the coldest month varies from around 15° C in the sub-mountain zone to less than 10° C above 2,000 m. Snow occurs above 3,000 m, with frequent winter frost. The average annual precipitation ranges from 500 to 1,000 mm.
The tropical mountains of the south-eastern part of the Himalaya, between 1,000 to 1,500 m and 4,000 m, show an annual precipitation of more than 1,000 mm, sometimes more than 2,000 mm. There is a distinct dry season of three to five months in the sub-alpine zone of the eastern Himalayas, with the mean temperature of the coldest month above 15° C. Everywhere else, the dry season, if it occurs, is very short. The mean temperature of the coldest month rapidly decreases with increasing elevation. Permanent snow is encountered at altitudes above 4,500 to 5,000 m.
The tropical rainforest that occurs at the eastern Himalayan foothills is very wet owing to the monsoon. Everywhere the annual rainfall sums up to more than 1,000 mm and often more than 2,000 mm, e. g. in Bhutan approximately 5,000 mm. There is a short dry season, generally one to four months. Temperatures are always high.
Tropical moist deciduous forest
The rainfall of the tropical moist deciduous forest is generally between 1,000 and 2,000 mm with a dry season of three to six months. Temperatures are always high, with a mean temperature of the coldest month slightly lower than 20° C.