On July 1, mountaineer Rasul Kadorov was climbing Arête des Cosmiques in the Mont Blanc massif at 3,750 meters when he captured one of the most extraordinary — and terrifying — lightning warning signs ever caught on video. The footage shows the air around him visibly fizzing as static electricity built up between the ground and storm clouds directly above him. Seconds later, lightning struck. Here’s the science behind this unusual phenomenon.