The mountains north of Kathmandu provide a diverse selection of trekking opportunities, many of which are within a day's drive of the metropolis. The Langtang Valley, the sacred mountain lake of Gosaikunda, and the undulating sherpa farming of Helembu are the main attractions. The Lantang region is an excellent choice for trekkers who either have a limited amount of time or who want to avoid the crowds of the Annapurna and Everest regions.
The Langtang region is located in the Rasuwa(Rasuwagadhi) district, which is home to the Tamang ethnic group, who are known for their traditional skills and way of life in Nepal's upper hills.
WHEN TO TREK
In general, it is the same as the rest of Nepal, however snowfall is heavy in the ganga-la, upper lantang valley, and near Lauribina-la in the winter, and there are hordes of leeches in the lower region during the monsoon, and it is hot in the summer due to the low elevation.
note : check the weather conditions locally or with guide/porter before attempting to cross any high passes .(mainly in wintter)