Bangladesh (; Bengali: , pronounced [balade] (listen)), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 163 million people in an area of either 148,460 square kilometres (57,320 sq mi) or 147,570 square kilometres (56,980 sq mi), making it one of the most densely populated countries in the world. Bangladesh shares land borders with India to the west, north, and east, and Myanmar to the southeast; to the south it has a coastline along the Bay of Bengal. It is narrowly separated from Bhutan and Nepal by the Siliguri Corridor; and from China by 100 km of the Indian state of Sikkim in the north. Dhaka, the capital and largest city, is the nation's economic, political, and cultural hub. Chittagong, the largest seaport, is the second-largest city. The official language is Bengali, one of the easternmost branches of the Indo-European language family.

Bangladesh forms the sovereign part of the historic and ethnolinguistic region of Bengal, which was divided during the Partition of India in 1947. The country has a Bengali Muslim majority. Ancient Bengal was an important cultural centre in the Indian subcontinent as the home of the states of Vanga, Pundra, Gangaridai, Gauda, Samatata, and Harikela. The Mauryan, Gupta, Pala, Sena, Chandra and Deva dynasties were the last pre-Islamic rulers of Bengal. The Muslim conquest of Bengal began in 1204 when Bakhtiar Khalji overran northern Bengal and invaded Tibet. Becoming part of the Delhi Sultanate, three city-states emerged in the 14th century with much of eastern Bengal being ruled from Sonargaon. Sufi missionary leaders like Sultan Balkhi, Shah Jalal and Shah Makhdum Rupos helped in spreading Muslim rule. The region was unified into an independent, unitary Bengal Sultanate. Under Mughal rule, eastern Bengal continued to prosper as the melting pot of Muslims in the eastern subcontinent and attracted traders from around the world. Mughal Bengal became increasingly assertive and independent under the Nawabs of Bengal in the 18th century. In 1757, the betrayal of Mir Jafar resulted in the defeat of Nawab Siraj-ud-Daulah to the British East India Company and eventual British dominance across South Asia. The Bengal Presidency grew into the largest administrative unit in British India. The creation of Eastern Bengal and Assam in 1905 set a precedent for the emergence of Bangladesh. In 1940, the first Prime Minister of Bengal supported the Lahore Resolution with the hope of creating a state in eastern South Asia. Prior to the partition of Bengal, the Prime Minister of Bengal proposed a Bengali sovereign state. A referendum and the announcement of the Radcliffe Line established the present-day territorial boundary of Bangladesh.

In 1947, East Bengal became the most populous province in the Dominion of Pakistan. It was renamed as East Pakistan with Dhaka becoming the country's legislative capital. The Bengali Language Movement in 1952; the East Bengali legislative election, 1954; the 1958 Pakistani coup d'tat; the Six point movement of 1966; and the 1970 Pakistani general election resulted in the rise of Bengali nationalism and pro-democracy movements in East Pakistan. The refusal of the Pakistani military junta to transfer power to the Awami League led by Sheikh Mujibur Rahman led to the Bangladesh Liberation War in 1971, in which the Mukti Bahini aided by India waged a successful armed revolution. The conflict saw the 1971 Bangladesh genocide and the massacre of pro-independence Bengali civilians, including intellectuals. The new state of Bangladesh became the first constitutionally secular state in South Asia in 1972. Islam was declared the state religion in 1988. In 2010, the Bangladesh Supreme Court reaffirmed secular principles in the constitution.Bangladesh is a unitary parliamentary constitutional republic based on the Westminster system. Bengalis make up 98% of the total population of Bangladesh, and the large Muslim population of Bangladesh makes it the third-largest Muslim-majority country. The country consists of eight divisions, 64 districts and 495 subdistricts. It maintains the third-largest military in South Asia after India and Pakistan; and has been a major contributor to UN peacekeeping operations. A middle power in the Indo-Pacific, Bangladesh is an emerging economy ranked as the 41st-largest in the world by nominal GDP, and the 30th-largest by PPP. It hosts one of the largest refugee populations in the world due to the Rohingya genocide. Bangladesh faces many challenges, including the adverse effects of climate change, poverty, illiteracy, corruption,demonstrations, and authoritarianism. However, the poverty rate has halved since 2011. Once a historic center of the muslin cloth trade, Bangladesh is now one of the world's largest modern garment exporters. Its economy has constantly been among the fastest growing economies in the 21st century.

A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.

Thunderstorms result from the rapid upward movement of warm, moist air, sometimes along a front. However, some kind of cloud forcing, whether it is a front, shortwave trough, or another system is needed for the air to rapidly accelerate upward. As the warm, moist air moves upward, it cools, condenses, and forms a cumulonimbus cloud that can reach heights of over 20 kilometres (12 mi). As the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earth's surface. As the droplets fall, they collide with other droplets and become larger. The falling droplets create a downdraft as it pulls cold air with it, and this cold air spreads out at the Earth's surface, occasionally causing strong winds that are commonly associated with thunderstorms.

Thunderstorms can form and develop in any geographic location but most frequently within the mid-latitude, where warm, moist air from tropical latitudes collides with cooler air from polar latitudes. Thunderstorms are responsible for the development and formation of many severe weather phenomena. Thunderstorms, and the phenomena that occur along with them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, and flash flooding caused by heavy precipitation. Stronger thunderstorm cells are capable of producing tornadoes and waterspouts.

There are three types of thunderstorms: single-cell, multi-cell, and supercell. Supercell thunderstorms are the strongest and most severe. Mesoscale convective systems formed by favorable vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the cloud-to-ground lightning that accompanies them. Several means are used to study thunderstorms: weather radar, weather stations, and video photography. Past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earth's atmosphere, thunderstorms have also been observed on the planets of Jupiter, Saturn, Neptune, and, probably, Venus.