This week, A rare weather event amazed people along Portugal’s coast, as a “roll cloud” moved over popular beaches during an ongoing heatwave. The unusual sight, which looks like a giant tube-shaped wave in the sky, was caught on camera and quickly spread across social media.

As reported by EuroNews, the event took place on Monday while Portugal continued to face soaring temperatures. The roll cloud was spotted stretching across multiple coastal areas, stunning onlookers and sparking conversation online.

In the viral video, a thick cloud appears to roll in from the ocean towards the beach, followed by strong winds that catch many people off guard. The footage has already gained over 20,000 views and plenty of reactions from surprised viewers.

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"Holy canoly! Is this the storm front that will give Europeans a respite from the heatwave in a few days?" wrote one person.

Another shared their memory, saying, "It's interesting, because they used to be very common here in Northern Portugal back when my parents were kids (60s-70s) and then they disappeared until yesterday."

“Wow, it's like a wave!” a third person said, while someone else added, “So ominous looking!”

What is a roll cloud?

A roll cloud is a type of arcus cloud, long, low, and tube-shaped, that appears to spin on its horizontal axis. Although they may look threatening, roll clouds are not linked to tsunamis or hurricanes.

These clouds often form when a cooler air mass moves underneath warm, moist air. This temperature difference, along with sea breezes, can create the dramatic cloud shape. They are usually seen near thunderstorms but are not commonly observed.

The rare roll cloud arrived as mainland Portugal experienced extreme weather conditions over the weekend. According to EuroNews, Sunday saw a mix of unexpected weather events, sudden rain showers, intense thunderstorms, and even hail, especially in the country’s interior regions.

With temperatures expected to keep climbing, Portugal's National Civil Protection Authority has issued alerts and safety recommendations for the public. Authorities have also warned of a “Very High” to “Maximum” risk of wildfires in the interior North, Centre, and Algarve regions.

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