During the daytime, the cool air flows from the sea towards the land, because at this time, the land gets heated faster than the water. It generates a low-pressure area above the land as compared to air over the sea. Hence, the air from the high-pressure area moves towards the low-pressure area.

During the night, cool air from the land flows back to the sea because the land gets cooled down rapidly at night and the pressure of the air above the land becomes higher than the air above the sea. Hence, there is a reverse flow of air.