the Himalayan climate is the Southwest Monsoon. This is not so much the rain of the summer months as the wind that carries the rain. Different rates of heating and cooling between the Central Asian continent and the Indian Ocean create large differences in the atmospheric pressure prevailing above each. In the winter, a high-pressure system forms and remains suspended above Central Asia, forcing air to flow in the southerly direction over the Himalayas. But in Central Asia as there is no substantial source for water to be diffused as vapour, the winter winds blowing across South Asia are dry. In the summer months the Central Asian plateau heats up more than the ocean waters to its south. As a result, the air above it rises higher and higher, creating a zone of low pressure. Off-shore high-pressure systems in the Indian Ocean push the moist summer air inland toward the low-pressure system. When the moist air meets mountains, it rises and upon subsequent cooling, its moisture condenses and is released as rain, typically heavy rain. The wet summer monsoon winds cause precipitation in India and all along the layered southern slopes of the Himalayas. This forced lifting of air is called the orographic effect. 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