The Dooars or Duars are the foothills of the eastern Himalayas in North-East India around Bhutan. Duar means door and the region forms the gateway to Bhutan from India. There are 18 passages or gateways through which the Bhutanese people can communicate with the people living in the plains. This region is divided by the Sankosh River into the Eastern and the Western Dooars. The Western Dooars is known as the Bengal Dooars and the Eastern Dooars as the Assam Dooars. Dooars is synonymous with the term Terai used in Nepal and northern India and form the only nitrate rich plain in India. The Dooars region politically constitutes the plains of Darjeeling Himalayas, the whole of Jalpaiguri district and Alipurduar district. The altitude of Dooars area ranges from 90 to 1,750 m. Innumerable streams and rivers flow through these fertile plains from the mountains of Bhutan. The major river is the Teesta besides many others like the Jaldhaka, Murti, Torsa, Sankosh, Dyna, Karatoya, Raidak, and Kaljani rivers, among others. Monsoon generally starts from the middle of May and continues till the end of September. Winters are cold with foggy mornings and nights. Summer is mild and constitutes a very short period of the year. Dooars is the ideal place in Bengal for monsoon travelling.