For fair weather trekkers out there that prefer a dry and warm trek there are two major trekking seasons in Nepal. These are from February through to May and September through to November.
February - May
February to May is a popular time because of the clear, bright days that appear around this period. Just coming out of winter you can still expect the occasional short showers, but most days will be fairly stable and dry. Expect this period to be busy in the Everest region as this is the time of year when most Everest summit attempts occur. That being said, if you're into the mountaineering scene, this is a great time to actually meet people attempting the summit and to feel the activity and buzz surrounding the climbing expeditions. Look out for the spectacular Rhododendrons on display during April!
September - October
September to October is the most popular time of the year for trekkers as it provides the most stable and clear weather. This is a bonus as most treks offer stunning vistas which, on a clear day, are simply spectacular. Although not the warmest time of the year, this period provides a pleasant temperature for trekking and the nights do not get super cold like they do in winter. You will have to contend with a fair amount of traffic though as the popular routes get very busy around this time, however, there is the option to take lesser known routes that will get you off the beaten track and away from the crowds. Although usually clear, storms occasionally hit during this period and you should bring suitable gear in case of this.
Off peak seasons
November - January
November through to January is the coldest period on the Nepalese calendar, however, for intrepid travellers out there, it can still be trekked. Although very cold, the weather is generally fairly stable and dry. The coolness of the weather will very much depend upon how high you want to trek. If you are going to Everest Base Camp for example, then expect overnight temperatures of around -20 to -30 degrees Celsius. However, if you stay down in the valleys the temperatures will remain fairly moderate and, if you're the hardy type, you will have no problem. Although far less crowded, please remember that many of the popular routes are closed during this period and the days will be much shorter.
June - August
June through to August is the wettest period in the Himalayas thanks to the monsoon season. Brought on by the warm, moist air coming off the Indian Ocean, the monsoon period is characterized by short, sharp downpours. The tea houses and trails begin to empty out in June and only the hikers looking to trek high are seen during these months. Even if you are trekking high you will get rain, particularly in wet regions like Everest. Not many foreign trekkers hike during the monsoon period as mud, rain, leeches and, most importantly, lack of mountain views, put most hikers off. Although not the best time to trek in Nepal, if this is the only period you can go then we would suggest trekking in one of the rain-shadow areas like the Annapurnas where it remains slightly drier during this period.
Whilst it's possible to trek all year-round in Nepal, the best time to trek in Nepal is in the peak seasons as they are warmer and provide the best opportunity for clear vistas.
Most tour companies will not trek during the off-peak seasons and you will need to find alternative guidance. At Kandoo we can arrange private treks during the off-peak seasons but would advise only experienced trekkers to trek Nepal in the winter period as the temperatures get very low and many routes will be snow covered.