Spain, Portugal and some parts of France were hit by widespread power outages on Monday, April 28. Millions of residents were left millions without due to the power outage described as "exceptional & extraordinary" by Spanish power distributor Red Electrica's head of operations Eduardo Prieto. While the cause of the unprecedented event is still under investigation, Spain’s Prime Minister Pedro Sanchez said a “strong oscillation” in the European grid was behind the outage. Portuguese energy company REN suggested that extreme temperature variations, caused by a rare atmospheric phenomenon, known as "induced atmospheric vibration", could be the reason behind the power outage.