section_path: Climate/Winds
section_name: Winds
paragraph_text: Winds
  
  The vast size, huge altitude range, and complex topography of the Himalayas mean they experience a wide range of climates, from humid subtropical in the foothills, to cold and dry desert conditions on the Tibetan side of the range. For much of the Himalayas—in the areas to the south of the high mountains, the monsoon is the most characteristic feature of the climate and causes most of the precipitation, while the western disturbance brings winter precipitation, especially in the west. Heavy rain arrives on the southwest monsoon in June and persists until September. The monsoon can seriously impact transport and cause major landslides. It restricts tourism – the trekking and mountaineering season is limited to either before the monsoon in April/May or after the monsoon in October/November (autumn). In Nepal and Sikkim, there are often considered to be five seasons: summer, monsoon, autumn, (or post-monsoon), winter, and spring.
  
  Using the Köppen climate classification, the lower elevations of the Himalayas, reaching in mid-elevations in central Nepal (including the Kathmandu valley), are classified as Cwa, Humid subtropical climate with dry winters. Higher up, most of the Himalayas have a subtropical highland climate (Cwb).
  
  The intensity of the southwest monsoon diminishes as it moves westward along the range, with as much as 2,030 mm (80 in) of rainfall in the monsoon season in Darjeeling in the east, compared to only 975 mm (38.4 in) during the same period in Shimla in the west.
  
  The northern side of the Himalayas, also known as the Tibetan Himalaya, is dry, cold, and generally windswept, particularly in the west where it has a cold desert climate. The vegetation is sparse and stunted and the winters are severely cold. Most of the precipitation in the region is in the form of snow during the late winter and spring months.
  
  Local impacts on climate are significant throughout the Himalayas. Temperatures fall by 0.2 to 1.2 °C for every 100 m (330 ft) rise in altitude. This gives rise to a variety of climates, from a nearly tropical climate in the foothills, to tundra and permanent snow and ice at higher elevations. Local climate is also affected by the topography: The leeward side of the mountains receive less rain while the well-exposed slopes get heavy rainfall and the rain shadow of large mountains can be significant, for example, leading to near desert conditions in the Upper Mustang, which is sheltered from the monsoon rains by the Annapurna and Dhaulagiri massifs and has annual precipitation of around 300 mm (12 in), while Pokhara on the southern side of the massifs has substantial rainfall (3,900 mm or 150 in a year). Thus, although annual precipitation is generally higher in the east than in the west, local variations are often more important.
  
  The Himalayas have a profound effect on the climate of the Indian subcontinent and the Tibetan Plateau. They prevent frigid, dry winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents. It also forms a barrier for the monsoon winds, keeping them from traveling northwards, and causing heavy rainfall in the Terai region. The Himalayas are also believed to play an important part in the formation of Central Asian deserts, such as the Taklamakan and Gobi.