Best Time to Visit Nepal
Nepal has a typical monsoonal, two-season year. The dry season runs from October to May and there's the wet (monsoon) season from June to September. Autumn (September to November) and spring (March to May) bring almost perfect weather and are definitely the best times to come to Nepal.
October to November, the start of the dry season, is in many ways the absolute best time. With the monsoon only recently finished, the countryside is green and lush, the air is sparkling clean and the Himalayan views are near perfect. Furthermore, the weather is still balmy. There are some important and colorful festivals to enjoy, though the Dasain festival in October can be disruptive if you are on a tight schedule. For obvious reasons this is also the high tourist season but in recent years, due to the political problems, even Nepal's 'high season' has been pretty quiet.
The best season to visit Nepal is after the monsoons that end in August, and before the winter sets in. The months between September and December are the most preferred ones by the visitors. The rains wash the dusty tracks and the valley looks magnificent with blooming flowers. Post -Monsoon Nepal welcomes you with flower-laden plains and brimming rivers. It is humid in plains at that time but it is still better than the scorching heat of the summers.
It is best to visit hilly areas in summers; that is, the month of May and June. The average temperature at that time hovers around 22-25 Celsius. Nights are a bit chilly in the lower Himalayan region but are comfortable. Mountainous areas are extremely unsafe in the Monsoons. The persistent rains make the hilly tracts slippery. The landslides are very common in the monsoons. Again in the post-monsoon months, you can start for the hill tours.
In winters, most of the hilly areas become out of bound due to very heavy snowfall and avalanches. But if you are fond of snowfall then you can opt for lower Himalayan regions that look beautiful in the blankets of snows.