The Madrid region was hit by a powerful hail storm on Monday evening, with heavy rainfall bringing roads to a standstill, causing problems on a number of lines on city’s underground Metro system and causing flight diversions at Barajas airport.

Firefighters responded to more than a thousand call outs, most of them for minor issues such as fallen tree branches or flooding in garages and basements. Spain’s meteorological agency AEMET recorded more than 9,300 lightning strikes in six hours.

During the extreme weather event, which lasted 20 minutes, the Socialist Party (PSOE) mayor of Arganda del Rey, Pedro Guillermo Hita Téllez, wrote on Twitter: “Trying to stabilise the situation and give an account of urgent requirements. The flash flood has been terrible. All services are working at full capacity to normalise [the situation]. Be alert to instructions.” On Tuesday, the city council will open an office for locals to assess the damage caused by the storm.

Hours before the storm, AEMET issued an orange alert for rain and storms, indicating a significant risk. As well as Arganda del Rey, the other areas most affected by the storm were Valdemoro, Pinto, Rivas, Getafe, Fuenlabrada and Madrid city, emergency services told EL PAÍS.

According to meteorologist Benito Fuentes, strong storms such as these ones are common in August. “The rain has been fairly heavy but it is not unusual for this time of the year. At the end of summer, the atmosphere is unstable, which causes air to rise for dynamic reasons, not thermal ones. This leads to quite strong rainfall and storms,” he told EL PAÍS by phone.

The heavy rain led to traffic jams, with many lanes blocked. The storm also wreaked havoc on Madrid’s Metro underground rail network, with numerous suspensions.

This is the first weather crisis to happen under Madrid’s new regional premier, the conservative Popular Party’s Isabel Díaz Ayuso, who was sworn into office two weeks ago thanks to support from the center-right Ciudadanos (Citizens) and far-right Vox. During the storm, Ayuso wrote on Twitter that she was in contact with the mayors of Arganda del Rey, Getafe and Madrid.

Weather conditions will return to normal on Tuesday in Madrid region according to AEMET, which has issued a special warning for showers and heavy storms in the east of the peninsula and the Balearic Islands.