Bangladesh: Weather Overview
Bangladesh experiences a tropical monsoon natured climate characterised by hot, wet summers and a prominent dry season in the cooler months. Bangladesh features a wide range of seasonal variations in rainfall, moderately warm temperatures, and high humidity; however, the local climatic disparities throughout the country are very minimal.
Instead of having four distinctive seasons, Bangladesh has only three; generally recognized as a hot, humid summer from March to June; a cool, rainy monsoon season from June to October; and a cool, dry winter season from October to March. Throughout the entire country, the coolest month is January with temperatures averaging near 26ºC and April being the warmest with temperatures ranging anywhere from 33ºC to 36ºC. The typical climate of Bangladesh is also one of the wettest in the world, with most areas receiving more than 1525mm of rain a year and areas near the hills receiving 5080mm. However, most rainfall occurs during the monsoon; from June to September and little in winter from; November to February.
Bangladesh has warm temperatures right through the year, with comparatively little discrepancy from month to month. In Dhaka, the average January temperature is about 19°C, and the average May temperature is about 29°C.
Winds throughout Bangladesh are mainly from the north and northwest in the winter, gusting softly at one to three kilometres per hour in northern and central areas and three to six kilometres per hour near the coast. From March to May, aggressive thunderstorms, generate winds of up to sixty kilometres per hour. Throughout the forceful storms of the early summer and late monsoon season, southerly winds of more than 160 kilometres per hour cause waves to peak as high as 6 meters in the Bay of Bengal, which can bring devastating downpours to the coastal areas.
Precipitation and Humidity
Heavy rainfall is a distinctive feature of Bangladesh. With the exemption of the comparatively dried out western region of Rajshahi, where the annual precipitation is approximately 1600mm, the majority of the country receives at least 2000mm of rainfall per year. Because the locality of the nation just south of the foothills of the Himalayas, where monsoon winds turn west and northwest, the region of Sylhet in north-eastern Bangladesh obtains the maximum average precipitation. From the years of 1977 to 1986, annual rainfall in that particular region varied between 3280mm and 4780mm per year. Average daily humidity ranged from March lows of between 45 and 71 per cent to July highs of between 84 and 92 per cent.
Bangladesh is one of the most flood-prone countries in the world. Basically, it's the flood plain where the nationâs two largest rivers; the Ganges and the Brahmaputra transmit spring snowmelt from the towering Himalayan Mountains to the sea. Bangladesh being mostly formed of the Gangetic delta will be severely impacted if sea-levels rise as a result of the greenhouse effect.
About 80 per cent of Bangladesh's rain falls throughout the course of the monsoon season. The monsoons effect from the disparities between low and high air pressure areas that result from discrepancy heating of land and water. During the hot months of April and May hot air rises over the Indian subcontinent, creating low-pressure areas into which hasten cooler, moisture-bearing winds from the Indian Ocean. This is the southwest monsoon, initiating in June and generally lasting through until September. Dividing against the Indian island, the monsoon flows into two branches, one of which strikes western India. The other travels up the Bay of Bengal and over eastern India and Bangladesh, crossing the plain to the north and northeast before being turned to the west and northwest by the foothills of the Himalayas.
Bangladesh is prone to shattering cyclones, initiating over the Bay of Bengal, in the periods of April to May and September to November. These cyclones are often attended by swelling waves, which have been known to cause great damage and loss of life. They can create winds with speed of 161 to 241 kilometres per hour piling up the waters of Bay of Bengal to crests as high as 20 feet that crash with remarkable force onto the coastal areas and offshore islands. Since the early 18th century, when records were first kept, more than one million people have been killed in such storms. Between 1947 and 1988, thirteen relentless cyclones hit Bangladesh, causing enormous loss of life and property. In May 1985, for example, a severe cyclonic storm packing 154 kilometre-per-hour winds and waves 4 meters high flounced into south-eastern and southern Bangladesh, killing more than 11,000 persons, damaging more than 94,000 houses, killing some 135,000 head of livestock, and damaging nearly 400 kilometres of critically needed embankments. The cyclone of November 1970 however, in which about 500,000 lives were lost in Bangladesh, was one of the worst natural disasters of the country in the 20th century.
Apart from Cyclones, other natural misfortunes, such as floods, tornadoes, and tidal bores devastate the country, particularly on the coastal belt, almost every year. Annual monsoon flooding results in the loss of human life, damage to property and communication systems, and a deficiency of drinking water, which leads to the spread of disease. In 1988 two-thirds of Bangladesh's sixty-four districts attributed widespread flood damage in the wake of curiously heavy rains that flooded the river systems. Millions were left homeless and without potable water. Half of Dhaka, including the runways at the Zia International Airport was flooded. About 2 million tons of crops were reported destroyed, and relief work was rendered even more challenging than usual because the flood made transportation of any kind exceedingly difficult.