The country experienced a major heatwave this Sunday, leading to unexpected situations and even rare phenomena, particularly along the coastal areas.
The northern coastal region, especially the beaches from Póvoa de Varzim, Vila do Conde, and even Figueira da Foz, was unexpectedly hit by a rare atmospheric phenomenon.
This event might have been hard to believe if not for the numerous videos that beachgoers eagerly recorded and shared on social media.
The explanation for the occurrence is provided by a page dedicated to climate and environment content, which describes the phenomenon as a roll cloud.
“Today, a rare phenomenon caught the attention of many Portuguese along the coast: a large roll cloud formed over the sea and was sighted in several areas of the country […] Despite its impressive appearance—resembling a giant wave in the sky—this type of cloud is not related to tsunamis. It is merely a rare atmospheric formation caused by contrasts between air masses and sea breezes”, the page explains.
Images of a phenomenon that appeared this Sunday on some Portuguese beaches were shared on social media, showing what looked like a wave from various angles, but known as a ‘volutus’.
Notícias ao Minuto | 19:54 – 29/06/2025
This type of cloud is long and tubular, moving horizontally as if “rolling” over the ocean. The phenomenon is extremely rare, especially in Portugal, but it is not dangerous. It forms when warm air clashes with cold air and instead of rising, it expands horizontally.
The phenomenon was witnessed at beaches such as Póvoa de Varzim, Vila do Conde, and Praia da Torreira in Aveiro.
In the gallery above, you can watch an impressive video of the moment, recorded by a beachgoer at Praia do Furadouro in Ovar.
Despite being rare, it’s not the first occurrence. Australia is a frequent location
Although the moment took everyone by surprise, with many unaware of what this peculiar cloud was, this is not the first time a similar situation has occurred in the country.
The meteorological platform recalls that in 1999, a similar event took place in the Algarve, causing a “real panic” situation.
“At the time, several people believed they were witnessing a tsunami. They spoke of a ‘giant wave on the horizon’ and fled the beaches en masse. In the end, it was an ‘optical illusion, caused by weather conditions,'” it adds.
Despite generally being a rare phenomenon, it occurs frequently in the southern part of the Gulf of Carpentaria in Northern Australia, the MeteoPT notes. This is the only known location where roll clouds can be predicted and regularly observed, due to the configuration of its territory and sea. In this country, however, the phenomenon is popularly known as the ‘morning glory cloud’.
Extreme heat in Portugal
It should be remembered that this Sunday was marked by extreme heat, prompting the IPMA to issue warnings, with red-level alerts in Alentejo, Vale do Tejo, and Beira Baixa. The forecasts indicated some unpredictability, with the possibility of scattered showers and thunderstorms, particularly in the inland regions.
Portugal is facing a hot and dry weather situation due to a mass of air coming from North Africa and this Sunday, June 29, was one of the hottest days, with several districts under a red alert.
