Massive power outage leaves Spain and Portugal in the dark. What caused it?

Train services were suspended, hospitals and emergency services switched to backup generators, and metro systems suffered sudden breakdowns after a massive power outage hit Spain, Portugal, and parts of France near the Spanish border on Monday. Spain has declared a state of emergency in what is described as Europe’s biggest power failure. Notably, Portugal’s grid operator REN said a ‘rare atmospheric phenomenon’ caused sharp temperature swings, which led to widespread shutdowns

Explainers