Met office statistics show that the frequency of depressions and cyclones in the Bay of Bengal has declined between 1891 and 2013 despite the rise in surface sea temperature. High sea-surface temperature in the Bay of Bengal is needed for depressions and cyclones that eventually lead to rainfall in Bangladesh. A seasonal monsoon flooding is essential for the good harvest of crops and fish. However, such depressions or cyclones can sometimes lead to disastrous floods. Some severe cyclones have hit the Bangladesh shores in 1963, 1970, 1991, 2007 and 2009, while many more moved towards the Andhra coast of India and the Myanmar coast after lashing at the Bangladesh coast.