October – November is the start of the dry season and is the most popular time to visit Nepal as the monsoon has recently finished, leaving a green and lush countryside, fresh and clean air, and clear views of the Himalayas.
From December – February the temperature is very cold but visibility is still good. With fewer tourists on the trails, this can be the preferred time to visit. However, the cold can make high altitude treks more strenuous than normal. Some treks will be closed due to snow.
March – May is the second most popular time to visit. The weather is warmer and the visibility is still good, though not as crystal clear as between October to November. Nepal’s flowers, however, come alive at this time of year.
June – September is the monsoon season. While you can still trek during this time, the options are limited due to the rains and heat.