The difference in air pressure causes wind. Wind blows from a region of higher pressure to a region of lower pressure. The difference in the air pressure and the rate of flow of air is directly proportional to each other.
As sunlight falls on the earth's surface, the land area gets heated up more quickly, in comparison to the ocean water bodies. As a result of this, the warm air rises up in the atmosphere, carrying moisture, and it eventually moves towards the region of low pressure over the ocean by the wind and this warm air then sinks over the cooler water surface. <u>Due to this unequal heating of the surface of the earth, the wind occurs</u>.