Nepal climate varies according to its season. Autumn and spring are the two most favorable seasons for Trekking in Nepal. Autumn starts from early September to early December and brings in clear weather with sunny days and warm nights. Whereas spring starts from the beginning of March to the end of May with occasional rain falls. From June to September, is the monsoon season.
Trekking is generally difficult and uncomfortable as the climate of Nepal at this time of year brings about hot weather and rain falls almost every day. The trails become muddy. Moreover, the mountains are usually obscured by cloud. There are, however, possibilities for summer trekking in the trans-Himalayan regions of Mustang, Dolpo and Tibet. These regions lie in a rain-shadow and therefore receive significantly less precipitation.