The climate of Nepal largely depends upon the attitudinal features according to which it is divided into five climatic zones viz: the tropical and subtropical zone lying below 1,200 meter altitude, the cool, temperate zone lying in between altitude of 1,200 to 2,400 meters
The climate of Nepal largely depends upon the attitudinal features according to which it is divided into five climatic zones viz: the tropical and subtropical zone lying below 1,200 meter altitude, the cool, temperate zone lying in between altitude of 1,200 to 2,400 meters; the cold zone lying between altitude of 2,400 to 3,600 meters; the subarctic climatic zone of lying between altitude of 3,600 to 4,400 meters and the arctic zone lying above altitude of 4,400 meters. Nepal has a wide range of altitudinal variation ranging from 70 meter above the sea level to 8848 meter above the sea level. Basically, the Geography of Nepal has divided it wholly into three main regions the Himalayan Region, Mountain Region and the Terai region from north to south direction.
The Himalayan massif dominating the northern part of the country ranging from east to west also plays vital role in the climatic alteration. Along with the climatic facto the altitude also affects the vegetation pattern and precipitation. Climate of Nepal can also be divided into four parts viz: pre-monsoon, summer monsoon, post monsoon and winter monsoon. If we talk about the monsoon Nepal mainly face summer monsoon and winter monsoon are rarely occurred. Summer monsoon usually starts from June with continuous rainfall for several days and ends at September. The northwest ward moment of the moisture laden air blowing from the Bay of Bengal brings bursts out the summer monsoon in Nepal. Conversely, in the winter, the great Himalayan range prevents the outbursts of cold air from Inner Asia from reaching southern Nepal which makes the winter dry in Nepal. The northern Rain shadow side of the Himalayan massif especially the Tibetan plateaus receives very less rain fall hence making it the drier region. Whereas the east and the south facing slope receives the precipitation due to the moisture created by the gradual increase of the slopes.
The pre monsoon period in Nepal occurs between the April to May and with the temperature of about 40 degree centigrade in the lowland of the country. The summer monsoon starts with lightning and thunderstorm from June and lasts up to September. During the period decrease in precipitation occurs from southeast to northwest direction. Post monsoon commences from September and by mid- October it stops precipitation bringing into cool and dry climate up to December. From December starts the winter monsoon brings short rain fall in lowlands and snowfall in the high land caused by the strong North easterlies wind.
It is cold and you will need to be prepared, but the air is very clear providing the best mountain views.
Days are increasingly warm and the rhododendrons are in bloom. Mist and clouds are not uncommon.
The monsoon season. It will rain every day, although generally in the evening and night. The hills turn lush and green and at higher elevations the alpine plants will bloom. Visibility can be mixed.
The most pleasant trekking season where days are warm, but not hot; there is little chance of snow and skies are clear.