<P> 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, dry desert conditions on the Tibetan side of the range . </P> <P> For much of Himalayas--that on the south side of the high mountains, except in the furthest west, the most characteristic feature of the climate is the monsoon . Heavy rain arrives on the south - west 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 . </P> <P> 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). </P> <P> In the furthest west of the Himalayas, in the west of the Kashmir valley and the Indus valley, the South Asian monsoon is no longer a dominant factor and most precipitation falls in the spring . Srinagar receives around 723 millimetres (28 in) around half the rainfall of locations such as Shimla and Kathmandu, with the wettest months being March and April . </P>

Write a short note on origin of himalayas