Nepal’s climate varies according to elevation. The Terai of southern Nepal has a tropical monsoon climate characterized by rainy summers and the southwest winds of the monsoon, and almost dry winters. In the Middle Himalayan valleys the amount of precipitation varies with the extent of exposure to the rain-bearing monsoon winds. In the Kathmandu Valley the average rainfall is about 2,300 mm (about 90 inches), most of which occurs from June to September. Between elevations of 500m and 2,700 m there is a warm temperate climate; between 2,700m and 3,000m a cool temperate climate prevails, and between 3,500m and 4,100m summers are cool and winters are very cold. Above 4,100m a cold, alpine climate prevails.
The best time to visit Nepal is the start of the dry season in October-November; the weather is balmy, the air is clean, visibility is perfect and the countryside is lush and green following the monsoon. April-May, the tail end of the dry season, is the second-best period: the weather is warm and many of Nepal’s wonderful wild flowers are in bloom, including the national flower, the rhododendron.
During these periods of October-November and April-May, and in alpine areas, overnight and early morning temperatures are often below 0 degrees Celsius, but with clear sky and bright sun, daytime temperatures usually rise to 15-20 degrees Celsius, very pleasant conditions for trekking.
Naturally, as is the case with most mountain ranges around the world, weather can be quite unpredictable, and warm rays of sun can easily change into rain or snow, and the temperature can easily drop below zero in a matter of minutes. As a result, we keep a keen eye on changes of weather and advise our clients accordingly, while expecting that everyone is well prepared for all four seasons, which can occur on the same day.