Spring (between March – May): The temperature is mildly warm in low lands while moderate in higher altitudes with plenty of opportunities to have tryst with the mountain views. It is also the time for flowers to blossom and the national flower of Nepal – rhododendron sweeps the ascending altitudes with its magnanimous color and beauty.
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. The rain spreads the pleasantness around with lush green vegetation.
Autumn (between September – November): This is the best tourist season in Nepal with the summer gone by and the winter to set in. The weather is highly pleasant so are the mountain views. This is the peak season for trekking as mountain views are guaranteed so better book your flight in advance. This is also the season of festivities 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 good for trekking in lower elevations. The morning and night is cold and the days are warm when sunny.
Nepal is the country of extremes. The low-land plains of the Terai can have tropical temperatures and also the mosquitoes. The Himalayas can get to sub-zero temperatures, but the sun blaze 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.
* Spring season ranges between 16-23 Degree Celsius (61-73 Degree Fahrenheit)
* Summer season ranges between 23-25 Degree Celsius (73-77 Degree Fahrenheit)
* Autumn season ranges between 15-24 Degree Celsius (59-75 Degree Fahrenheit)
* Winter season ranges between 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.
Travel Tips: 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.