Climatic condition

Nepal has tremendous variation in climate. Nepal has five climatic zones, broadly corresponding to the altitudes. The tropical and subtropical zones lie below 1,200 metres (3,937 ft), the temperate zone 1,200 to 2,400 metres (3,937 to 7,874 ft), the cold zone 2,400 to 3,600 metres (7,874 to 11,811 ft), the subarctic zone 3,600 to 4,400 metres (11,811 to 14,436 ft), and the Arctic zone above 4,400 metres (14,436 ft).Nepal experiences five seasons: summer, monsoon, autumn, winter and spring. The Himalaya blocks cold winds from Central Asia in the winter and forms the northern limit of the monsoon wind patterns. Precipitation generally decreases from east to west with increasing distance from the Bay of Bengal, source of the summer monsoon. The monsoon is preceded by a buildup of thunderstorm activity in the hills that helps farmers irrigate rice seedbeds.  Significant failure of monsoon rains historically meant drought and famine while above-normal rains still cause flooding and landslides with losses in human lives, farmland and buildings. The monsoon also complicates transportation with roads and trails washing out while unpaved roads and airstrips may become unusable and cloud cover reduces safety margins for aviation. Rains diminish in September and generally end by mid-October, ushering in generally cool, clear, and dry weather, as well as the most relaxed and jovial period in Nepal. By this time, the harvest is completed and people are in a festive mood. The two biggest and most important Hindu festivals-- Dashain and Tihar (Dipawali)--arrive during this period, about one month apart.