This rare phenomenon was recorded at Praia de Buarcos beach, where a dark cloud band tens of kilometers long rolled menacingly towards the shore, bringing strong winds and obscuring the sun.

Videos recently circulating on social media show many beachgoers hastily gathering their belongings and fleeing the beach, as winds began to gust strongly and thick, rolling dark clouds formed like a “sky wall.”

Image of the giant “tsunami cloud” sweeping onto the Portuguese coast on July 4. Photo: Daily Mail “It’s crazy to witness this rolling cloud in Northern Portugal,” a beachgoer wrote on X. “It felt like watching a tsunami in a movie!” Another expressed: “It was like a disaster movie. The whole sky collapsed in just a few minutes. We thought there was a real tsunami.”

Many tourists gathered their belongings and fled Praia de Buarcos beach when the “tsunami cloud” appeared on July 4. Photo: Storyful Meteorologists said this is a very rare “roll cloud” phenomenon, also known as a “tsunami cloud.” “Tsunami clouds” form when a cold air current from a thunderstorm pushes warm, moist air below upwards, causing water vapor to condense into a horizontal, tube-shaped cloud band, sometimes stretching for hundreds of kilometers.

This cloud formation appeared after temperatures in Northern Portugal exceeded 42°C in the last week of June (previously reaching 46.6°C at one point), combined with high humidity and sea breezes, creating ideal conditions for “tsunami clouds” to form. Some local sources reported that the cloud band might have stretched over 145 km along the coast from Vila do Conde to Figueira da Foz. After the “tsunami cloud” appeared, the area experienced heavy rain, lightning, and even hail. Although it did not cause major damage to people, the “tsunami cloud” phenomenon caused panic among many and became a hot topic on social media platforms. The rare “tsunami cloud” phenomenon occurred as Europe continues to experience extreme weather events with unusual dark clouds and torrential rains, while record heat also causes wildfires in many places.