Geography and climate
Main articles: Geography of West Bengal and Climate of West Bengal
Many areas remain flooded during the heavy rains brought by monsoon
National Highway 31A winds along the banks of the Teesta River near Kalimpong, in the Darjeeling Himalayan hill region.
West Bengal is on the eastern bottleneck of India, stretching from the Himalayas in the north to the Bay of Bengal in the south. The state has a total area of 88,752 square kilometres (34,267 sq mi). The Darjeeling Himalayan hill region in the northern extreme of the state belongs to the eastern Himalaya. This region contains Sandakfu (3,636 m or 11,929 ft)—the highest peak of the state. The narrow Terai 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 Sundarbans 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 or Pôdda, while the other flows through West Bengal as the Bhagirathi River and Hooghly River. The Farakka barrage over Ganges feeds the Hooghly branch of the river by a feeder canal, and its water flow management has been a source of lingering dispute between India and Bangladesh. The Teesta, Torsa, Jaldhaka and Mahananda rivers are in the northern hilly region. The western plateau region has rivers such as the Damodar, Ajay and Kangsabati. The Ganges delta and the Sundarbans area have numerous rivers and creeks. Pollution of the Ganges from indiscriminate waste dumped into the river is a major problem. Damodar, another tributary of the Ganges and once known as the “Sorrow of Bengal” (due to its frequent floods), has several dams under the Damodar Valley Project. At least nine districts in the state suffer from arsenic contamination of groundwater, and an estimated 8.7 million people drink water containing arsenic above the World Health Organisation recommended limit of 10 µg/L.
West Bengal’s climate varies from tropical savanna in the southern portions to humid subtropical in the north. The main seasons are summer, rainy season, a short autumn, and winter. While the summer in the delta region is noted for excessive humidity, the western highlands experience a dry summer like northern India, with the highest day temperature ranging from 38 °C (100 °F) to 45 °C (113 °F). At nights, a cool southerly breeze carries moisture from the Bay of Bengal. In early summer brief squalls and thunderstorms known as Kalbaisakhi, or Nor’westers, often occur. West Bengal receives the Bay of Bengal branch of the Indian ocean monsoon that moves in a northwest direction. Monsoons bring rain to the whole state from June to September. Heavy rainfall of above 250 cm is observed in the Darjeeling, Jalpaiguri and Cooch Behar district. During the arrival of the monsoons, low pressure in the Bay of Bengal region often leads to the occurrence of storms in the coastal areas. Winter (December–January) is mild over the plains with average minimum temperatures of 15 °C (59 °F). A cold and dry northern wind blows in the winter, substantially lowering the humidity level. However, the Darjeeling Himalayan Hill region experiences a harsh winter, with occasional snowfall at places.(copy from wiki)