Nepal's climate varies with its topography and altitude, ranging from the tropical to the arctic. The low-land Terai region in the tropical southern part of the country, has a hot and humid climate that can rise above 45 Degree Celsius (113 Degree Fahrenheit) during summer. The mid-land regions are pleasant almost all the year round, although winter nights are cool. The northern mountain region has an alpine climate with considerably lower temperature in winter, especially , at altitudes above 3300m. There are normally four seasons are considered in Nepal, each of which has its own particular attraction to offer.
Trekking in Nepal can be undertaken throughout the year. with four distinct seasons each with different attractions to offer:
Spring (between March – May)
Springtime temperatures are mildly warm in the lowlands and moderate at higher altitudes, with plenty of opportunities for clear mountain views. It is also the time for flowers to blossom, and the national flower of Nepal – rhododendron - coats the mountainsides with its colorful beauty throughout the spring.
Summer (between June – August)
This is also the monsoon season in Nepal. The weather is hot and wet at times. It rains almost everyday with occasional thunderstorms in the evening, though mornings are often clear and you can expect beautiful sunrises.
This is the favorite season to trek in the arid rain shadow areas like Upper Mustang, Dolpo and Kailash. This season is also recommended for forest researchers and botanists. The advantages of trekking in the summer months are the uncrowded trails and the less cold in the high mountains.
Autumn (between September – November)
This is the best trekking season in Nepal. The weather is very pleasant and clear so the mountain views are the best. This is the peak season for trekking as mountain views are guaranteed so it’s wise to books your flights well in advance. This is also the season of festivals as Nepal celebrates the biggest Hindu festivals - Dashain followed by Tihar.
Winter (between December – February)
The weather is cool and the sky is clear with occasional snowfalls at higher elevations. This season is best for trekking in lower elevations generally below 3200m.. The mornings and nights are cold but daytime temperatures are mild when it is sunny.
Temperature and Rainfall
Nepal is the country of extremes. The low-land plains of the Terai can have tropical temperatures and also mosquitoes, particularly in the summer months. The Himalayas can get to sub-zero temperatures, but the sun can bring some warmth during the day, even in the mountains. The temperature of Kathmandu goes below 1 Degree Celsius (34 Degree Fahrenheit) in winter and rises to an average of 25 Degree Celsius (77 Degree Fahrenheit) in summer.
The average temperature in Kathmandu during the four seasons:
- Spring season: 16-23 Degree Celsius (61-73 Degree Fahrenheit)
- Summer season: 23-25 Degree Celsius (73-77 Degree Fahrenheit)
- Autumn season: 15-24 Degree Celsius (59-75 Degree Fahrenheit)
- Winter season: 9-12 Degree Celsius (48-54 Degree Fahrenheit)
During the rainy monsoon season between June to August, it rains to an average between 200-375 millimeters in Kathmandu. There is occasional rainfall during the other seasons too. In an average, 1300 millimeters of rain falls in Kathmandu every year.
Monsoon in Nepal is not the typical monsoon of Asia. Rains usually occur during the night-time leaving the sky clean and clear by the morning making the Himalayan view even more dramatic. Some parts of the Himalayas in Manang, Mustang and Dolpo are in rain-shadow areas; the mountains are high enough to block the clouds. Tibet's high travel season also corresponds to Nepal's monsoon.