When is the best season for Nepal Trekking?

Sep to November (Autumn season)
This is officially regarded as the best trekking seasons in Nepal with excellent weather and outstanding panoramic mountain views. The weather is very fine and pleasant with clear visibility. Since the beginning of the October up to November is said to be the most preferred season (Peak Season) for the trekkers.
March – May (Spring season)
March to May is officially regarded as the best trekking seasons in Nepal with excellent weather and outstanding panoramic mountain views.The spring (season of the flowers, the rhododendron), this is the second finest trekking season and one can feel the fewer crowds of tourists on the trekking trails. This season remains quite moderate in temperature and especially the rhododendrons are blossomed in its full measure along with clear mountain views. The temperatures are gently warm in the lowlands and little cold at higher altitudes and the sky remains crystal clear.
June –August (summer season)
This is the most preferable season for the limited areas like Mustang, Upper Manang, Dolpo and Simikot. These are places where the touch of monsoon can not reach due to the proximity of areas to the mountains. This season is also recommended for forest researchers and botanist. The other trekking places like Annapurna regions and Jomsom part are also significantly less rainy areas and short trek in these areas are highly recommended.
December to Mid February (Winter season)
The weather in these seasons remains awesomely cool and the sky is clear with occasional snowfalls at higher elevations, the stars at night glitter with nocturnal ecstasy. This season is best for trekking in lower elevations generally below 3200m. The weather is at its finest condition, in the mornings and nights are cold but relatively daytime temperature is mild when it is sunny. The trek to Low altitude area such as Annapurna region, Langtang Helambu region, Everest region and it’s surroundings villages are the best to do. Even Everest base camp can be organized in winter.
The advantages of winter trekking is that we find the trekking trails and villages with few trekkers and where one can better enjoy the natural beauty and Himalayan silence in the absence of crowds