Temperature differences at the Earths surface occur wherever there are differences in surface substances. Water for example, has a much greater heat capacity than soil and rock. When the Sun heats it, it takes much longer for its temperature to rise. On a warm summer day along the coast, this differential heating of land and sea leads to the development of local winds called sea breezes.
As air above the land surface is heated by radiation from the Sun, it expands and begins to rise or convect, being lighter than the surrounding air. To replace the rising air, cooler air is drawn in from above the surface of the sea. This is the sea breeze, and can offer a pleasant cooling influence on hot summer afternoons when further inland the heat may become oppressive. A very hot summer Sun may cause a sea breeze of up to 15 mph along the coast, felt in decreasing strength 20 to 25 miles inland.
Since the sea breeze owes its existence to the enhanced heating of the land under the Sun, it follows that at night, when the land cools faster than the sea, a land breeze may develop. In this case, it is air above the warmer surface water that is heated and rises, pulling in air from the cooler land surface.