The best time for Nepal is October to November or February to April. Visit Nepal during October and November, as this is the time when you can expect better visibility, the air is fresh, and the weather is perfect and that the Nepalese most important festivals(Dashain & Tihar) are marked during that season . May to June is also a good time to travel although the weather is hot and dusty- you can live with that; wear a mask and a Nepali Topi (Cap) and learn how Nepalese get along with this period. December to January is the winter season in Nepal, which is also a good time to travel; the climate and visibility is good. Snow jackets and sweaters are recommended. Mansoon starts from Mid June to September; traveling during this period is not advisable unless you are the one who loves best in everything or finds best from anything. Just bring your raincoat during that season, and have a blast!