Spanish prime minister Pedro Sánchez said a nationwide blackout of this scale had never happened before in Spain. He added that the underlying cause remains unclear.

According to Spain’s meteorological agency, AEMET, temperatures across the country were between 60 and 70 degrees Fahrenheit around the time of the power outages. By the end of the day, highs had climbed to between 82 and 87 degrees.

A blackout has brought much of Spain and Portugal to a standstill, affecting millions of people. The Spanish power distributor calls it “exceptional and extraordinary."