A sea-breeze (or onshore breeze) is a wind from the sea that develops over land near coasts. It is formed by increasing temperature differences between the land and water which create a pressure minimum over the land due to its relative warmth and forces higher pressure, cooler air from the sea to move inland.
A sea-breeze front is a weather front created by a sea-breeze, also known as a convergence zone. The cold air from the sea meets the warmer air from the land and creates a boundary like a shallow cold front. When powerful this front creates cumulus clouds, and if the air is humid and unstable, cumulonimbus clouds, the front can sometimes trigger thunderstorms. If the flow aloft is aligned with the direction of the sea breeze, places experiencing the sea breeze frontal passage will be benign, or fair, weather for the remainder of the day. At the front warm air continues to flow upward and cold air continually moves in to replace it and so the front moves progressively inland. Its speed depends on whether it is assisted or hampered by the prevailing wind, and the strength of the thermal contrast between land and sea. At night, the sea-breeze usually vanishes.
Thunderstorms caused by powerful sea breeze fronts frequently occur in Florida, a peninsula surrounded on both the east and west by the Atlantic Ocean and Gulf of Mexico, respectively. No matter which direction the winds are blowing, they are always off the water, thus making Florida the place most often struck by lightning in the United States, and one of the most on Earth. On especially calm days with little prevailing wind, sea-breezes from both coasts may collide in the middle, creating especially severe storms down the center of the state. These storms also tend to produce significant hail due to the tremendous uplift it causes in the atmosphere. In Florida, a sea-breeze pushed by prevailing winds may also continue past the land and out over the water at night, creating spectacular cloud-to-cloud lightning shows for hours after sunset.