Bhola cyclone: A 240 km/h (150 mph) tropical cyclone hits the densely populated Ganges Delta region of East Pakistan (now Bangladesh), killing an estimated 500,000 people in one night.

The 1970 Bhola cyclone was the deadliest tropical cyclone on record, as well as one of the deadliest humanitarian disasters ever recorded. It struck East Pakistan and India's West Bengal on 12 November 1970. At least 300,000 people died in the storm, possibly as many as 450,000, primarily as a result of the storm surge that flooded much of the low-lying islands of the Ganges Delta. Bhola was the sixth and strongest cyclonic storm of the 1970 North Indian Ocean cyclone season.

A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean. A typhoon is the same thing which occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn or more.

The Ganges Delta is a river delta predominantly covering the Bengal region of the Indian subcontinent, consisting of Bangladesh and the Indian state of West Bengal. It is the world's largest river delta and it empties into the Bay of Bengal with the combined waters of several river systems, mainly those of the Brahmaputra River and the Ganges River. It is also one of the most fertile regions in the world, thus earning the nickname the Green Delta. The delta stretches from the Hooghly River in the west as far as the Meghna River in the east.