Bangladesh, formerly East Pakistan, is a very low-lying country at the head of the Bay of Bengal. Apart from the Chittagong hill district in the extreme southeast on the border with Myanmar and India's easternmost regions, the whole country lies below 180 m/600 ft.
Most of the country consists of the swampy plains of the great delta of the rivers Ganges and Brahmaputra. Aside from its border with Myanmar, all of the country's boundary is with India.
Bangladesh has a tropical monsoon climate with the same threefold division of the year as occurs in India. The cool season from November to February is here warmer than in much of India.
During the hot season from March until early June some rainstorms occur and these are often thundery. During the main rainy season of the southwest monsoon from June to September the rainfall is heavy and frequent.
Most of the country receives between 1,500-2,500 mm/60-100 in of rain a year and near the eastern border this rises to as much as 3,750 mm/150 in or more.
The rainfall is most reliable and frequent during the season of the southwest monsoon and is brought by shallow depressions in the northern Bay of Bengal.
Rainfall in the period September to November is less reliable but is occasionally very heavy and is usually associated with violent tropical cyclones. These severe storms, which bring very strong winds and torrential rain, develop at this time in the Bay of Bengal and are the most dangerous feature of the climate of Bangladesh.
The storm waves and sea surges raise the water level along the coast and in the numerous branching water courses of the delta so that widespread flooding of the low-lying areas occurs, adding to the devastation produced by the strong wind. Such storms have caused great loss of life and destruction of crops several times this century.
Although temperatures during the hot season are somewhat lower in Bangladesh than in some parts of India, the heat is made uncomfortable by the high humidity. This muggy, damp heat persists throughout the main rainy season.
The heat is rarely dangerous but is certainly unpleasant to visitors who are not acclimatized. There is no great difference in temperature conditions around the year from one part of the country to another.
During the hot season temperatures are a little higher inland (see the table for Dhaka, previously Dacca) than on the coast (see the table for Chittagong). Because of the greater cloudiness during the rainy season, average daily hours of sunshine are least between June and September, about four hours a day. During the rest of the year they average from six to eight hours.
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