Fallstreak holes typically develop in mid-level cloud layers made up of supercooled water droplets. These droplets remain in liquid form even though temperatures are below freezing. Under the right conditions, a small disturbance can trigger the droplets to freeze rapidly into ice crystals. Once that process begins, the surrounding liquid droplets evaporate, leaving behind a large circular or oval-shaped opening. As sunlight shines through the gap, it creates the glowing effect that makes the formation appear so dramatic from the ground.