As much of Europe battled a rare heat wave, beachgoers trying to cool off on the coast of Portugal were stunned by another surprising weather phenomenon. Videos taken across parts of the northern and central coast showed a dark,

A rare roll cloud was seen passing over several beaches in Portugal on Sunday, June 29. The phenomenon features a cloud that strongly resembles a tsunami quickly rolling over a space where two contrasting temperatures merge.

Roll clouds seen in Portugal following heatwave as temperatures hit over 107 °F with heavy rain, thunderstorms, and hail.