The sea breeze (or coastal breeze) is a local wind that blows from the sea towards the land during the day, caused by the differential heating of land and water. Land heats much faster than the sea under sunshine: by midday, the air over land is significantly warmer and rises, creating lower pressure. Cooler, denser air over the sea flows inland to fill the gap, producing a refreshing onshore wind that typically begins by late morning and peaks in the early afternoon.
Sea breezes can penetrate 20–50 km inland (sometimes more in tropical regions) and reach speeds of 15–30 km/h. The leading edge of the sea breeze — called the sea breeze front — acts like a miniature cold front: it can trigger cumulus cloud development and even thunderstorms where it converges with the ambient flow or collides with another sea breeze front from the opposite coast (as occurs in Florida and peninsular Malaysia).
Along Spain's Mediterranean coast, the sea breeze (virazón or marinada in Catalan) is a daily summer phenomenon that moderates coastal temperatures by 5–8 °C compared to inland areas. Barcelona, Valencia, and Málaga owe much of their summer comfort to this wind. At night, the process reverses: land cools faster, creating a gentle land breeze that flows from shore to sea. This land–sea breeze cycle is one of the most predictable local weather patterns and has been known to sailors and coastal communities since antiquity. Pollutants can be trapped in a recirculating sea-breeze cell, worsening air quality in some coastal cities.