Spain and Portugal are racing the setting sun as they respond to a massive, unexplained power outage that knocked out traffic lights, caused chaos on roads and in airports, and threatened to plunge tens of millions of people into darkness on Monday.

MADRID/LISBON (Reuters) -Power started returning to parts of the Iberian peninsula late on Monday after a huge outage brought parts of Spain and Portugal to a standstill, grounding planes, halting public transport,

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.