The best time to travel to Nepal is spring and autumn. This is the time generally to expect good weather and clear views.
Spring (March to May) is the time when the flower blooms. It is so wonderful that the surroundings become so colorful with different kinds of the flower blooming. This is the most suitable time for trekking in Nepal. The days are warmer and the nights are cold. For the high altitude trekking, it is highly favorable time. It is also the wonderful time for the tours.
Autumn (September to November) is the festival time in Nepal. The greatest festivals of Nepal fall in autumn. Teej, Dashain and Tihar festivals are celebrated in autumn. If you love cultural exploration, you will catch the excellent moment. This is neither hot nor cold time, which is the great time to travel in Nepal. The Himalayas are favorable to trek with clear views and good weather.
Generally, monsoon (July-August) is not regarded as a favorable time to travel in Nepal, but there are some of the trekking regions, that are highly suitable to trek in monsoon time. Mustang region treks and Dolpo region treks are monsoon favorable trekking in Nepal.