Nagarkot is a year-round destination but the mountain views that justify the trip are strongly seasonal. The two best windows are autumn (October to November) and spring (February to April). In autumn, the monsoon has washed the sky clear and the air is crisp; you can sometimes see peaks all the way to Dhaulagiri on a good October morning. In spring, rhododendron forests below the ridge are in bloom.
Monsoon season, from June to September, brings clouds that reliably obscure the mountains — sometimes for days at a time. The forest is lush and green and the landscape is beautiful, but you may wait a week without seeing a single peak. Winter (December to January) can be excellent for views on clear days but is cold at night, and frost and occasional snow are possible on the ridge.
Weekends bring day-trippers up from Kathmandu who crowd the view tower for sunrise but mostly leave by mid-morning. If you arrive on a Friday afternoon and stay until Sunday, you will share the viewpoints; midweek visits are significantly quieter.