About choosing a suitable season and date
Mid September to November: An ideal time for high altitude treks, with warm days followed by cooler evenings, and post-monsoon skies of great clarity. A very lush and verdant season.
December to February: High altitudes mean chillier days and cold nights, but lower altitudes still retain pleasantly warm daytime temperatures
March to May: Ideal for all altitudes when really warm days bring the huge tree Rhododendrons into bloom. As the monsoon season approaches, afternoon cloud cover will increase.
June to early September: Monsoon season when regular, heavy rain precludes much of Nepal apart from Mustang and Dolpo, which is within the Tibetan rainshadow area; visits to Mustang, Dolpo and Manaslu in the West, towards the end of the season, are also feasible.