Generally speaking, spring (Mar., April. and May) and autumn (Sept., Oct., and Nov.) are the best seasons to visit Nepal for trekking, climbing, and white-water rafting. Because during this season you'll enjoy the clear skies and great mountain views. But it also means during these peak seasons, the trails are most crowded compared with the low seasons. For the winter (Dec to Feb) and summer (Jun to Aug, monsoon) time, it is also worth a visit as there are fewer crowds though the weather may not be so good. Besides, winter is the best time to visit Chitwan as the temperature is good and the forests are less dense for better wildlife sightings. Our Nepal trip advisor will recommend the best itinerary for you according to your travel time.