Spring and autumn are the best travelling seasons in Nepal. The weather becomes clear in these seasons and you can explore the astonishing views. In Trekking, it is the perfect seasons to walk and ascending in the high altitude. In monsoon, it rains a lot and there is the possibility of several landslides and streams become enormous. But, there are rain shadow areas like Dolpo and Mustang region, that are the best area to trek in monsoon. Winter is a tough season to trek in the Himalayan region, however, the trek and tour in the lowland region is possible. You can visit Nepal all the seasons.