A massive power outage hit Spain and Portugal on Monday, knocking out traffic lights and forcing the evacuation of subway systems in both countries, among other disruptions. It is being blamed on a “rare atmospheric phenomenon,” reports said.

A graph on Spain’s electricity network website that shows power demand across the country indicated a steep drop at around 12:15 p.m. local time, from 27,500 megawatts to near 15,000, according to the Associated Press. 

“Due to extreme temperature variations in the interior of Spain, there were anomalous oscillations in the very high-voltage lines, a phenomenon known as induced atmospheric vibration,” REN, Portugal’s grid operator, was quoted as saying. “These oscillations caused synchronization failures between the electrical systems, leading to successive disturbances across the interconnected European network.”

REN reportedly described the incident as a “rare atmospheric phenomenon.” The Portuguese National Cybersecurity Center issued a statement saying there was no sign the outage was due to a cyberattack. 

People try to board a crowded bus after the subway stopped running in Lisbon, Portugal, on Monday, April 28, 2025.  (AP/Armando Franca)

Spanish airports were operating on backup electrical systems and some flights were delayed, according to Aena, the company that runs 56 airports in Spain including Madrid and Barcelona.

Lisbon Airport said on its website that “A general power cut may cause operation constraints” and urged travelers to “Contact your airline before heading to the airport.”

Both the Portuguese and Spanish governments convened emergency cabinet meetings to address the situation, according to Reuters. Residents in both countries told Sky News that they have observed people panic buying water and other supplies inside supermarkets.

A cook from a take-out food restaurant works in a dark kitchen with the aid of a phone’s flashlight during a power outage in Madrid on Monday. (Reuters/Susana Vera)

Spanish Prime Minister Pedro Sánchez also visited grid operator Red Eléctrica to follow efforts at restoring power. 

Eduardo Prieto, head of operations at Red Eléctrica, told journalists it was unprecedented, calling the event “exceptional and extraordinary.”

“Voltage has now been restored at substations in several areas of the north, south, and west of the Iberian Peninsula,” Red Eléctrica wrote on X. “This process involves the gradual energization of the transmission grid as the generating units are connected.” 

A view shows a dark metro station in Lisbon, Portugal, during a widespread power outage that struck Spain and Portugal around midday Monday. (Adri Salido/Anadolu via Getty Images)

“The causes are being analyzed, and all resources are being dedicated to addressing the issue,” it added. 

The Associated Press contributed to this report.