The cyclone is a violent tropical storm in which strong winds move in a circle with low pressure at the centre. It occurs in our country several times in the latter part of the year. And all of them originate in the Bay of Bengal and move towards Bangladesh and India. The cyclone is always accompanied by heavy rainfall and tidal bore. Sometimes the bore is so high and violent that it inundates the coastal districts of our country. The cyclone blows away houses and trees and the bore wash away everything killing thousands of people and cattle. The cyclone of 1970 killed more than 5 lakh people and the cyclone killed about two lakh people in 1991. Though the cyclone causes immense losses to the lives and properties in the coastal areas, it becomes weaker when it moves further to the north. The Sundarbans slow down the speed of the cyclone and protect greater Khulna and Jessore from its fury.