Circulations of air common along coasts, caused by a low-level pressure gradient due to the differential heating of land and sea. On summer days, the land surface heats more quickly than the adjacent sea, air rises over the land, moves over the sea at height, then subsides, producing a shallow convection cell and reducing the surface pressure over land and increasing it over the sea. The resulting pressure gradient from sea to land results in a gentle, cooling, landward ‘sea breeze’ whose maximum strength is usually developed by late afternoon. Land then cools more rapidly than the sea, and at night and in early morning the cooler land and relatively warmer sea produce a reverse-flow convection cell, with a seaward ‘land breeze’. The horizontal extent of well-developed land and sea breezes is typically limited to about 40 km from the coast, but associated air movements can often be detected over a much wider coastal belt.