The festival marks the summer solstice and the feast day of Saint John the Baptist. In Porto and across the Douro region, the evening of 23 June is characterised by large-scale public gatherings. Traditional food consumption is central to the event, specifically grilled sardines served on sourdough bread known as broa. This seasonal peak for Atlantic sardines coincides with their highest fat content, a requirement for traditional grilling methods over open charcoal fires.
Accompanying the sardines is caldo verde, a soup composed of potato purée, shredded kale, and slices of chouriço. The kale used is the Galician variety, which is finely sliced into ribbons. While the city remains active until dawn, most formal restaurants and shops close early to allow for street-based celebrations. Visitors should note that the use of plastic hammers and the launching of paper hot-air balloons are standard regional customs during these hours.
Following the festivities, the city observes a public holiday on 24 June. This day traditionally features the Rabelo Boat Regatta on the Douro River. These flat-bottomed vessels, formerly used to transport wine barrels from the upper Douro valley to the lodges in Vila Nova de Gaia, compete between the Cabedelo and the Ponte D. Luís I. The race is organised by the Confraria do Vinho do Porto and serves to maintain the historical maritime record of the Port trade.