West Bengal (Bengali: Poshchimbongo) sharing its borders with Bangladesh on its east, forms the ethno-linguistic region of Bengal. To its northeast lie the states of Assam and Sikkim and the country Bhutan, and to its southwest, the state of Orissa. To the west it borders the state of Jharkhand and Bihar, and to the northwest, Nepal.
The state has a total area of 88,752 square kilometres. The Darjeeling Himalayan hill region in the northern extreme of the state belongs to the eastern Himalaya. The narrow Terai or Duars region separates this region from the plains, which in turn transitions into the Ganges delta towards the south. The Rarh region intervenes between the Ganges delta in the east and the western plateau and high lands. A small coastal region is on the extreme south, while the Sundarban mangrove forests form a remarkable geographical landmark at the Ganges delta.
The Ganges is the main river, which divides in West Bengal. One branch enters Bangladesh as the Padma, while the other flows through West Bengal as the Bhagirathi River and Hooghly River. The Ganges delta and the Sundarban area have numerous rivers and creeks.
West Bengal's climate varies from tropical savannah in the southern portions to humid subtropical in the north. The main seasons are summer, rainy season, a short autumn, and winter. In early summer brief squalls and thunderstorms known as Kalbaisakhi, or Nor'westers, often occur. Monsoons bring rain to the whole state from June to September. Winter (December–January) is mild over the plains with average minimum temperatures of 15 °C (59 °F). However, the Darjeeling Himalayan Hill region experiences a harsh winter, with occasional snowfall at places.
Due to the great variation in altitude , the state has diverse flora and fauna. Forests make up 14% of its geographical area. West Bengal as a whole offers an astounding 820 species of birds.