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In Tramandaí, the city hall closed the Mirante Beira-Mar and piled sand to contain the water; in Atlântida Sul, lifeguard towers became submerged. The Navy issued a warning for the entire coast, from Mostardas to Florianópolis, of waves up to 3 meters, and there is also a polar air mass arriving.
The sea advanced forcefully over the coast of Rio Grande do Sul on May 21, 2026, a Thursday, knocking down part of a containment wall in Tramandaí, carrying away wooden walkways in Atlântida Sul, and flooding streets at Praia do Cassino. The damage was caused by a strong swell, associated with the action of an extratropical cyclone in the ocean, according to Climatempo, which left the sea rough and the tide high along the entire coast of Rio Grande do Sul.
The force of the waves changed the landscape of the shoreline, knocked down structures, and closed tourist spots in cities in the North and South regions of the state. In response to the situation, the Brazilian Navy issued a swell warning valid until the morning of this Friday, May 22, warning of waves up to 3 meters high in the stretch between Mostardas, in Rio Grande do Sul, and Florianópolis, in Santa Catarina. The advance of the sea frightened residents and required emergency actions from local city halls.
The sea damage in Tramandaí and the North Coast
For safety reasons, the city hall closed the Mirante Beira-Mar, one of the city’s most well-known tourist spots. The Department of Public Works isolated the damaged section and used sand to create an improvised barrier, in an attempt to contain a new advance of the sea over the urban structure while the tide remained high.
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The situation repeated itself on other beaches in the region. On the shore of Atlântida Sul, a district of Osório, the storm surge caused significant damage: part of the boardwalk collapsed in the area of the kiosks due to the impact of the waves, wooden pedestrian walkways were partially carried away by the water, and lifeguard towers were submerged. According to the Osório city hall, a complete assessment of the damages can only be made when the tide goes down and the sea recedes from the shore.
From Torres to Cassino: the advance of the sea along the coast
In Torres, at the extreme north of the state, the intense waves and high tide altered the landscape, causing the sea to advance over the sand strip and reduce the beach area. The scene of waves reaching close to structures and dunes became common throughout the day, recorded by residents and tourists who witnessed the phenomenon.
In the Southern Coast, at Praia do Cassino in Rio Grande, considered one of the largest beaches in the world in terms of length, residents were startled by the water advancing over the streets near the shore. Despite the scare caused by the sea invasion, the municipality did not report severe structural damage, unlike what happened on the Northern Coast. The difference in impact between the regions is linked to the geography of each stretch of the coast and the local intensity of the waves.
What is the extratropical cyclone that stirred the sea
According to Climatempo, this entire scenario is the result of the action of an extratropical cyclone in the ocean. This type of phenomenon is a low atmospheric pressure system, usually associated with the passage of a cold front, which generates extensive areas of strong winds over the sea. When these winds persist over the water’s surface, they transfer energy to the ocean and form larger-than-normal waves that propagate to the coast in the form of a storm surge.
It is important to understand that the extratropical cyclone does not need to be over the coast to cause damage. Even moving offshore, far from the coast, it can generate the maritime agitation that hits the beaches. This is exactly what happened in Rio Grande do Sul, where the system in the ocean caused the storm surge that knocked down walls and invaded streets, without necessarily having a storm over the cities affected by the sea’s advance.
The Navy’s alert and the cold front that comes with it
The Directorate of Hydrography and Navigation of the Brazilian Navy has issued bad weather warnings for different sections of the Brazilian coast, predicting waves up to 3 meters high. In addition to the section between Mostardas and Florianópolis, which covers the entire coast of Rio Grande do Sul and southern Santa Catarina, there was also an alert for the coast between Ilhabela, in São Paulo, and Campos dos Goytacazes, in Rio de Janeiro, showing that the phenomenon affects a large part of the South and Southeast coast of the country.
Along with the agitation of the sea, a new mass of polar air began to advance over Brazil on the same Thursday, dropping temperatures in several states and increasing the risk of frost in the Southern Region. In other words, in addition to the damage caused by the sea on the shore, the population of Rio Grande do Sul faced the arrival of intense cold, in a period of climatic instability that combined storm surge, strong winds, and a sharp drop in temperatures in just a few days.
Why the coast of Rio Grande do Sul suffers so much from storm surges
The coast of Rio Grande do Sul is particularly vulnerable to sea advances because of its geography. It is a low, sandy, and relatively flat coast, without many natural rocky formations that act as barriers against the waves. This makes urban structures built close to the shore, such as boardwalks, kiosks, and retaining walls, exposed to the force of the water during storm surge episodes like this week’s.
Coastal erosion is a recurring problem in the region, aggravated by increasingly frequent extreme weather events. Each strong storm surge tends to eat away part of the sand strip and pressure the shore constructions, requiring constant investments in recovery and containment. Episodes like the one in Tramandaí, where the wall had to be reinforced with sand urgently, illustrate the ongoing challenge of dealing with the sea’s advance in this part of the Brazilian coast.
The advance of the sea over the coast of Rio Grande do Sul is another chapter in the tense relationship between coastal cities and the ocean’s force. The damage in Tramandaí, Atlântida Sul, Torres, and Cassino shows how a storm surge caused by an extratropical cyclone, even distant at sea, can cause real damage and change the landscape of the shoreline in a few hours. With the tide still high and the cold arriving, the moment is one of attention and to follow official alerts.
Do you live on the coast of Rio Grande do Sul or have you witnessed a strong storm surge with the sea advancing over the streets? Do you think coastal cities are prepared to face these increasingly frequent events? Leave your comment, tell us how the situation is on your beach, and share the article with those who live on the coast or follow the weather and climate in the Southern Region.
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