Trekking is possible at any time of the year depending on where you go. Generally speaking, the best months to trek are September-November (Post-monsoon) and March-May (pre-monsoon). It is possible to trek throughout the year but trekkers must be aware that bad/freak weather can strike in any season. Below are details of trekking seasons in Nepal.
Autumn is the most popular time for trekking in Nepal. It is normally dry, stable and offers excellent climate, amazing mountain views and the weather is perfect. Temperatures are usually moderate during this period making it a good time for any higher and low altitude treks. It can be cold at night at higher altitudes, but not as cold as in the winter months. The day time temperatures are pleasantly cool. The Nepalese most important festivals (Dashain and Tihar) are marked during this season.
This season is noted for occasional snowfall only at higher altitudes. So, it’s ideal for trekking at lower altitude, generally below 3200m. Winter is very cold above 4,000 m and high mountain passes may be blocked by snow and ice. The high-altitude treks require good gear and experience in cold-weather conditions as temperatures at 5000m can drop below -20°C and heavy snow can fall. Below 2000 meter temperatures can be quite spring like though valleys are often filled with fog or haze.
The temperature is quite moderate in this season. Varieties of wild flowers especially the rhododendrons are in complete blossom. It is mildly warm at lower altitudes and at higher altitudes, over 4000m. The Mountain Views are excellent while the temperature is quite moderate. This is Nepal’s second trekking season and the main trails can get crowded.
Summer (Early June-July)
This is the favorite season to trek in the rain shadow areas like Upper Mustang, Dolpo and Kailash. This season is also recommended for forest researchers and botanists. . It is recommended to carry raincoats and insect repellents when trekking during these summer months.
During this season you can trek in the rain-shadow areas north of the Himalayan like Upper Mustang and Dolpo. These places are out of reach of the rain clouds because of the high mountains and are unaffected by the monsoon. Note that the Monsoon is not consistently rainy. Avoid low elevation treks in the areas of Annapurna and eastern Nepal.