All the climatic zones of the world are to be found within the small compass of Nepal- from tropical jungles of the Terai to the ice-clad Himalayan Giants and the desert-like, high valleys of the inner Himalayas. The fact that the altitude can vary from 230 to 29,030 feet within the space of merely 100 miles explains why Nepal has no one dominant climatic feature.

The climates and the seasons are influenced by two principles factors: the first is the gigantic Himalayan wall running from east to west, varying in elevation from 16,000 to 29,000 feet and forming a mighty climatic barrier between central Asia and the Indian continent.

The second factor is the Monsoon. The monsoon period is the most important season for the Nepalese since the crop growth and harvest depends upon its length and intensity. Yet the monsoon brings not merely blessings but also hardships, causing the rivers to flood, wrecking the laboriously constructed terraces and repeatedly causing gigantic mountains slides which wipe out many villages from the face of the Earth. A number of festivals are connected with the monsoon , such as that in honour of the Red Machindranath before the monsoon period, and the great festival of Indra Jatra in August/September . Sacrifices are offered to the Gods for rain, accompanied by prayers that no storm may damage the harvest. The Monsoon originates in Bay of Bengal and its warm and humid air reaches Nepal at the beginning of June. It ends as a rule between the end of September and middle of October and, during this time, brings some 80% of the country's annual rainfall. The distribution of rainfall is different for each region depending on the location and the altitude. In general , the participatation level is lower in the west than in the east, which is explained by the close proximity of the eastern Nepal to the Bay of Bengal.

The Himalayas present such as impenetrable barrier to the monsoon those extreme differences both in climate and vegetation are found to the north and south of the main ridge. In the South, where the annual rainfall is over 150 inches, dense primeval forests cover the mountain slopesd to heights of about 13,000 feet. A mere 15 miles further north, the valleys are arid and desert-like, the climate permitting only meager vegetations. A spite of this, these high valleys have produced a considerable number of settlements at the heights between 8,000 and 14,000 feet which have developed an "oasis' culture.