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

Winds throughout Bangladesh are mainly from the north and northwest in the winter, gusting softly at one to three kilometers per hour in northern and central areas and three to six kilometers per hour near the coast. From March to May, aggressive thunderstorms, generate winds of up to sixty kilometers per hour. Throughout the forceful storms of the early summer and late monsoon season, southerly winds of more than 160 kilometers 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 nations locality 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 percent to July highs of between 84 and 92 percent.

Bangladesh is one of the most flood-prone countries in the world. Basically, it's the flood plain where the nation’s 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.

Monsoon Season

About 80 percent 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 in 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.