October to late November is the most popular season for trekking with most areas having crystal clear mountain views with excellent weather, the most moderate temperatures and the least rain.
March to the beginning of May is the best season for most wildlife, including rhododendron. The temperatures are moderate, though the views are more hazy than in autumn and there is more chance of intermittent rain. Later in May can start to get a bit hot, especially at lower altitudes.
Four treks in the rain-shadow area west of Annapurna; Rara Lake, Lower and Upper Dolpo and Upper Mustang, are best done from March through to October, ie if you’re coming in the monsoon season then trek here.
December to February is cold with snowfalls at higher elevations and, because mountain passes may be snowbound, we only recommend hiking at lower elevations, generally below 3,000m. These include 2 hikes close to Kathmandu, the Helambu Valley and the Kathmandu Valley Ridge treks, the Everest Panorama trek, 3 Annapurna area treks, Ghandurk, Ghalegaun and Ghorepani – Poon Hill, and one close to Langtang, the Tamang Heritage trek. Lots of other treks, eg the Pike trek, which are not on the data base, can also be arranged.
June to September is the monsoon period and the farmers are busy. Expect wet, warm and wild trekking during the rainy season, though you will see lush green valleys and luxuriant jungles (and encounter leeches).