the Satkhira subdivision of 24 Parganas district, and the Sundarbans) in 1882. Khulna had a pouroshava (municipal council) in 1884, which became a municipal corporation in 1984. Before 19 August 1947, Khulna District was part of undivided Bengal. Khulna first declared itself as part of India in 1947, and the Indian flag was flown on 15 August. Syed Mohammad Abdul Halim (an official of the Bengali civil service) requested Khulna's inclusion in Pakistan, and the boundary commission declared that the city was part of East Bengal. Sher e Bangla A.K.Fazlul Haq, Muslim League leaders Khan A Sabur, Advocate Hamidul Haq Chowdhury, A. F. M. Abdul Jalil, and Abdul Mojid Khan were also involved in the process. During the Bangladesh Liberation War, the Pakistan Army created the 314th ad hoc Brigade to hold Khulna. The city's Mukti Bahini fighters were part of sector 8 under the command of Major Abu Osman Chowdhury and, later, under Major Mohammad Abdul Monjur. Geography Khulna is Bangladesh's third-largest city, after Dhaka and Chittagong. It is in the south-western part of the country, on the Rupsha and Bhairab Rivers. The city covers , and Khulna District covers . Khulna is south of Jessore and Narail Districts, east of Satkhira District, west of Bagerhat and north of the Bay of Bengal. It is part of the Ganges Delta, the world's largest river delta. Sundarbans, the world's largest mangrove forest, is in the southern part of the delta. Tidal-flat ecosystems are adjacent to the city. Khulna is in the northern part of the district, and the Mayur River is the western boundary of its metropolitan area. Climate In the Köppen climate classification, Khulna has a tropical wet and dry climate. The city is hot and humid during summer, and pleasantly warm during winter. Khulna is significantly affected by the Monsoon of South Asia. Khulna gets less rainfall than other parts of Bangladesh, however, due to its location and the effects of the Sundarbans south of the city. Its annual average rainfall is , with about 87 percent falling between May and October. Khulna also receives heavy rain from cyclones which form in the Bay of Bengal. The city has an annual average temperature of , with monthly averages ranging from on January mornings to during April afternoons. Administration Khulna Municipal Council was founded on 12 December 1884. It became a municipal corporation in 1984, and a city corporation