thumb|300px|Sea breeze moving across the water (towards theviewer) in [[Hobart, Tasmania, Australia]]
thumb|250px|Lake/sea breeze and atmosphericdepth
A sea breeze or onshore breeze is a wind that blows in the afternoon from a large bodyof water toward or onto a landmass. By contrast, a landbreeze or offshore breeze is a wind that blows in the night from a landmass toward or onto a large bodyof water. Seabreezes and landbreezes are both important factors in coastal regions' prevailing winds.
Sea breeze and land breeze develop due to differences in created by the differing heat capacities of water and dryland. As such, seabreezes and landbreezes are more localised than prevailing winds. Since land heats up much faster than water under solar radiation, a seabreeze is a common occurrence along coasts after sunrise. On the other hand, dryland also cools faster than water without solar radiation, so the wind instead flows from the land towards the sea when the seabreeze dissipates after sunset.
The land breeze at nighttime is usually shallower than the seabreeze in daytime. Unlike the daytime seabreeze, which is driven by convection, the nighttime landbreeze is driven by convergence.
The term offshore wind refers to any wind over open water, which is related to but not synonymous with offshore breeze.
Causes
Sea breeze
The sea has a greater heat capacity than land, so the surface of the sea warms up more slowly than the surface of the land. The strength of the seabreeze is directly proportional to the temperature difference between the land and the sea. If a strong offshore wind is present (that is, a wind greater than ) and opposing the direction of a possible seabreeze, the seabreeze is not likely to develop.
Land breeze
The land forces the dying of seabreeze so the temperature of the land approaches that of the ocean. If the land becomes cooler than the adjacent sea surface temperature, the airpressure over the water will be lower than that of the land, setting up a landbreeze blowing from the land to the sea, as long as the environmental surface wind pattern is not strong enough to oppose it.
Sea breezes typically extend to a vertical depth of 1 to 2 kilometers and a horizontal distance of 10 to 100 kilometers from the coastline, with their strength and spatial reach directly determined by the magnitude of the land-sea temperature difference that is the fundamental cause of their formation. and one of the most on Earth. These storms can also produce significant hail due to the tremendous updraft it causes in the atmosphere, especially during times when the upper atmosphere is cooler such as during the spring or fall.
On calm summer afternoons with little prevailing wind, seabreezes from both coasts may collide in the middle, creating especially severe storms down the center of the state. These thunderstorms can drift towards either the west or eastcoast depending on the relative strengths of the seabreezes, and sometimes survive to move out over the water at night, creating spectacular cloud-to-cloud lightning shows for hours after sunset. Due to its large size, may also contribute to this activity by creating its own lakebreeze which collides with the east and westcoast seabreezes.
In Cuba, similar seabreeze collisions with the northern and southern coasts sometimes lead to storms.
Sea breezes in Southeast Australia
thumb|A sailing [[skiff during an afternoon seabreeze in the ]]
In the southeast Australian states of NewSouth Wales and Victoria, an intense seabreeze called the southerly buster causes an abrupt, squally southerly wind change, with gusts in excess of , in coastal cities such as Sydney in NewSouth Wales, south to Mallacoota, Victoria and Melbourne, as it approaches from the southeast, mainly on a hot day, bringing in cool, usually severe weather and a dramatic temperature drop, thus ultimately replacing and relieving the prior hot conditions. Marking the boundary between hot and cool air masses, the southerly buster is sometimes represented by a perpendicular to the coast.
The southerly buster is caused by the interaction of a shallow cold front with the blocking GreatDividing Range that aligns with the coast, as the coolair becomes trapped against the ranges. The mountains create a channelling effect as the southerly gale winds move across the NewSouth Wales coast, and frictional contrasts over the mainland and the ocean that disconnect the flow. Temperature changes can be dramatic, with falls of often occurring in a fewminutes.
Land breeze
Land breeze, which consists of coolair coming from the land, pushes the warmerair upwards over the sea. If there is sufficient moisture and instability available, the landbreeze can cause showers, or even thunderstorms, over the water. Overnight thunderstorm development offshore due to the landbreeze can be a good predictor for the activity on land the following day, as long as there are no expected changes to the weather pattern over the following . This is mainly because the strength of the landbreeze is weaker than the seabreeze.