Heavy rains, equivalent to several months of normal precipitation, fell in parts of the western Mediterranean over just a few days in late September and early October. The storm system affected northeastern Spain, near Barcelona, and southeastern France. This sequence of storms, which began in late September, has been described by some meteorologists as possibly marking the early stages of a cyclonic formation similar to those seen in tropical regions. The Mediterranean Sea has experienced similar weather events in the past, known as "medicanes." These are low-pressure systems that share some characteristics with tropical cyclones, such as strong winds and heavy rainfall. However, the phenomenon observed at the beginning of October appears to be a group of thunderstorms that formed from warm, humid air rising rapidly and organizing into a large convective system with its own vortex, according to some reports. Spanish meteorologist Juan Jesús González Alemán stated that there is no recorded precedent for this type of weather system in the Mediterranean. Italian physicist Guido Cioni, who created a video showing signs of rotation in the storm system, estimates that these thunderstorms caused a significant "mountain" of rain between Barcelona and Marseille from September 29 to October 5. The Saint-Hippolyte-du-Fort station in the Gard region recorded 374 mm of rain during the week, which is equivalent to seven months of precipitation in Paris. High temperatures in the Mediterranean Sea are believed to have contributed to the formation of these intense thunderstorms. On September 25, the average surface temperature of the Mediterranean exceeded 26 °C, a temperature not seen so late in the season since at least 1991, according to data from the European Copernicus service. With global warming, oceans absorb and retain excess heat over long periods, sometimes several years. This has led to Mediterranean temperatures reaching peaks around 28 °C during the summer, about 2 degrees higher than the average for the period 1991-2020. Cioni notes that these temperatures are closer to those found in tropical oceans than in mid-latitude seas.