Ask when to trek in the Himalaya and the short answer is October. Ask a longer question, about a particular range, a particular pass or a particular tolerance for cold and crowds, and the answer becomes much more interesting. The Himalaya and the ranges around it stretch across several climates, and the monsoon that soaks Nepal in July leaves Ladakh dry and the Karakoram in its best walking weather. This guide describes the four seasons as they apply to trekking, region by region, and how we choose between them.
The monsoon: June to September
The summer monsoon reaches eastern Nepal in early June and withdraws from the west in late September, and in between it delivers about 80 percent of the year’s rain to the southern side of the range. Trails are muddy, leeches are active below about 2,500 m, rivers run high, landslides close roads and the peaks are hidden for days at a time. Flights to Lukla are cancelled more often than they run. This is the season to avoid for the classic routes of the Everest, Annapurna and Langtang regions, though the lower valleys are green and almost empty, and the lodges that stay open are glad of company.
The exception is the rain shadow. North of the main crest, the monsoon clouds have already dropped their moisture, and the high desert valleys of Upper Mustang and Dolpo in Nepal, and above all Ladakh and Zanskar in India, have their main trekking season precisely when the rest of the Himalaya is under water. Ladakh’s passes, many above 5,000 m, are typically clear of snow from late June to mid September. Pakistan’s Karakoram follows the same logic: the treks toward the great glaciers and the base camps of the 8,000 m peaks are walked from June to early September, when the high camps are free of snow and the days are long. Kyrgyzstan’s Tien Shan, further north again, has a short summer window from July to early September before the passes close.
Post-monsoon: October and November
When the monsoon withdraws, it leaves behind the clearest air of the year. Dust and haze have been washed out, the views are sharp to the horizon, and the weather is stable for weeks. Days are mild at lodge altitudes and cold at night, dropping well below freezing above 4,000 m by November. Rivers are full but bridges are in place, and every lodge and campsite is open. This is the season most people picture when they imagine a Himalayan trek, and it is also the busiest: the popular trails and the flights into Lukla fill up, and prices for everything rise.
Timing within the window matters. Early October can still see the tail of the monsoon and occasionally a late cyclone tracking up from the Bay of Bengal, which in 2014 brought heavy snow to the Annapurna region with tragic results. Late November is colder and quieter, and the high passes begin to hold snow, but the skies are usually the best of the year. Bhutan’s main trekking season runs across the same months, with the trails toward Jomolhari and the higher routes at their best in October and early November.
Winter: December to February
Winter in the Himalaya is dry, clear and cold. At Namche Bazaar, at 3,440 m, January nights routinely fall to minus 10 degrees or below, and above 5,000 m minus 20 is ordinary. The reward is solitude: trails that carry hundreds of walkers a day in October are almost empty, and the mountain views, if anything, improve. The cost is a changed set of possibilities. Lodges above about 4,000 m close or operate a skeleton service, and the high passes that link valleys, such as the Thorong La at 5,416 m, the Larkya La at 5,106 m or the Cho La at 5,420 m, are frequently blocked by snow or dangerous with ice. Winter storms are rare but severe when they arrive.
For experienced walkers with a warm bag and a flexible plan, winter treks that stay in a single valley, such as the walk up to Everest Base Camp without crossing passes, or the Langtang valley, are entirely feasible and profoundly quiet. Winter is also the season for the lower and middle hills of Nepal, for the foothills of Sikkim and for parts of the Indian Himalaya below 3,000 m, where clear skies and comfortable daytime temperatures make for easy walking. In Ladakh, the frozen river walk along the Zanskar in January and February is a specialised undertaking that depends entirely on ice conditions.
Pre-monsoon: March to May
Spring is the second main season. The air warms steadily, the rhododendron forests of eastern Nepal and Sikkim flower from March into April, and the high passes reopen through April and May as the snow melts. Days are longer and warmer than in autumn, which suits high camps and long pass days. The compromise is visibility: haze accumulates through the dry months and by May the views from lower altitudes can be milky, with afternoon cloud and thunderstorms becoming more frequent as the monsoon approaches. Above 4,000 m the mornings are still generally clear. Spring is also the mountaineering season, so the Everest region is busy with expedition traffic and the lodges of the upper Khumbu fill early.
The Japanese Alps run to a different calendar altogether. The mountain huts open from roughly early July to early October, with a heavy rainy season in June and early July and typhoons possible from August into September. Late July and August are the reliable window for the high traverses, and the autumn colour in late September and early October is spectacular but brief.
Matching the season to the trek
The choice comes down to a few questions we ask every time. Does the route cross a high pass? If so, October and November or April and May, and in winter only with an alternative planned. Is the area in the rain shadow? If so, the summer months open up while the rest of the range is closed. How much do crowds matter? Late November, early December and late February offer clear skies with a fraction of the traffic. How cold can the group tolerate at night, and is the sleeping bag rated for it? And how much time is there in the itinerary for weather, which in every season means building in spare days? A trek chosen with these questions in mind will almost always be walked in the right month, and a trek chosen by the calendar alone will sometimes be walked in the rain.