Trekking in Nepal can be undertaken throughout the year depending on the region. Nepal has tremendous variation in climates as there is a vast variation in altitude. The low land plain are sub tropical(600-1200m), the midland hills are warm temperate (1200-2100m) and cool temperate(2100-3300m)and the high mountains are Alpine(3300-5000m) and Tundra(5000-8848m). Mid of September to mid of December consider ever best season for trekking in Nepal.
Autumn Season (September-November) < Best Season >
Autumn is considered as the best season to trek in Nepal. You can experience the better visibility of tantalizing mountain, Green hills and excellent weather. Weather is generally clear with mild to warm days and cold nights. There are less possibilities of natural disaster, safe and excellent trekking can be experienced. Main Nepalese festival Dashain and Tihar are also marked in this season.
Winter Season (December- February)
In winter, Himalayan area get freeze with a mass of snow fall. Trekking can be challenging in the higher altitude because the trail can be covered with snow. Winter season is suitable for trekking in lower altitude below 3000m from sea level. The temperature of Himalayan region will be up to -18 degree Celsius, hilly region 0 to 5 degree Celsius whereas in plain region 10 to 15 degree Celsius.
Spring Season (March-May) <Good Season>
Trekking in spring is really a lovely as the hilly slopes will be seen as a garden of blooming flower with lush and an abundant green in the jungle with the view of Clear Mountain show you the really feel you like a right place at right time. Spring feels as a hunting paradise offers an excellent mountain views, Singing of birds and blooming a varieties of wild flowers. Weather will be mild warm at lower elevation bud cold at higher elevation. In spring, mornings are usually very clear whereas afternoon cloud brings showers rain.
Summer Season (June-August)
In summer, mornings are cloudy, afternoon and evening are mostly rainy. Trekking is very uncomfortable because the trial becomes risky, muddy, wet, warm and leech-infested. There is high chance of natural disaster mainly landslide in hilly region. If you trek, you must not forget to carry insect repellants. The temperature of Himalayan region will be 16 to 20 degree Celsius, hilly region 20 to 30 degree Celsius where as in plain region 34 to 39 degree Celsius. Although trekking is not good in major places but summer is best for botanists and researchers in forest and higher altitudes. Different places of Nepal like Manang, Mustang and Dolpo which is consider as a rain shadow area summer is the best time to trek. These rain shadow area will be neither hot nor cold.