Tourism License No. 1791
Best seasons to visit for trekking in Nepal, tours, adventure, and mountaineering in Nepal are autumn (Sept, Oct, Nov) and spring (March, April, May). These are the two most favorable and recommended seasons. In these seasons you will be rewarded by good weather, sunny and warm with clear blue sky and magnificent views. The spring however might get some occasional showers. During monsoon (June, July, Aug) the issue could be of less visibility, rain, muddy trails, and leech-infested trails. The mountains are hidden by clouds. However, in monsoon the hills turn lush and green; the higher valleys, mountains and meadows blossom with flowers and abundant vegetation, so for a keen botanist monsoon is blessing to trek in Nepal. You can also trek in winter (Dec, Jan, Feb) but the problem in winter is cold weather with snow-fall at higher elevations. Over the past few years, peak climbers and trekkers have found early winter (end of Nov until mid Dec) quite favorable time as snow gets harder and wind condition remains stabilized.
Nepal has some trans-Himalayan regions such as Mustang and Dolpo (Upper Mustang, Lower Mustang, Upper Dolpo, Lower Dolpo) towards north-west of Dhaulagiri Mountain range. These regions lie in rain shadow and do get very less precipitation as the cloud flowing from the south is blocked by the Himalayan range. So, trekking can be organized in this area even in summer/monsoon.
The trekking routes are crowded during main seasons, i.e. spring and autumn but during monsoon and winter the routes are not packed and you could enjoy rather best of nature. If you want to avoid the crowd trekking still in best time, starting your trek towards start or end of each best season is good idea, i.e. starting end of Feb to early March, starting towards end of May, starting mid September, starting towards end of November. Or you can choose to do remote are treks to avoid crowd on popular trails.
Nevertheless, because of effects of global warming the climate is changing world wide and there could always be likelihood of exception in these weather patterns. In best seasons also there could be swindling of bad weather and sometimes even in adverse months; weather turns out to be outstanding for trekkers.
Nepal has diverse climate and topography. The altitude ranges from 80m from sea level to 8,848m. While the southern plains are hot most of the year, temperature decreases gradually towards North as the altitude increases.
Autumn is the most favorable time to trek. Generally during autumn, the weather is clear with mild to warm days and cold nights. However, in the higher altitude, the nights drop into freezing temperature. In this season, the mountains views are surprisingly clear. This is also the season of festivities as Nepal celebrates the biggest Hindu festivals Dashain followed by Tihar.
The weather is cool and the sky is clear with occasional snowfalls at higher elevations. Daytime temperatures will be cooler; however, the nights obviously very cold. Days can be warm when sunny. It is also possible to trek during winter, from December until the end of February. The days are generally clear but occasional winter storms can bring snow as low as 2500m. This season is good for trekking in lower elevations. Trekking in high altitudes is more challenging due to weather during this time because of semi-regular snowfall followed by more winter storms.
As snow gets harder and wind condition remains stabilized in early winter (until mid Dec), climbing some of trekking peaks is possible. Climbing Mera peak, Island peak, Chulu, and trekking in Annapurna, Everest, Langtang in early winter have been quite popular over the past few years.
In the spring, the mornings are usually clear but afternoon cloud build-up brings occasional showers. The days are mix up with warm and rain, which displays wildflowers like rhododendrons. The whole country is lush and an abundant green at this season. This period instigate the second most popular and pleasant trekking season as this is rice-planting time. Late-march into April is especially beautiful. It is also a good time for climbing as the high passes are usually snow free and the mountain views are still clear in April. Up to May, the weather becomes hazy and disturbed with the clouds.
From June to September, is the monsoon season. Generally the morning is cloudy and cloud wisps form on random ridges and peaks. Trekking at this time of year is generally difficult and uncomfortable as the weather is hot and it rains almost every day. The trails become muddy and are often leech-infested and the mountains are usually obscured by cloud. During April and May, there is an expectation of thunderstorm, hail shower and strong winds among the fine periods. There are, however, possibilities for summer trekking in the trans-Himalayan regions of mustang, Dolpo and Tibet. These regions lie in a rain-shadow and therefore receive significantly less precipitation than the more southerly areas.