GRAND CANYON, AZ (WTXL / CNN) – The National Park Service shared this picture of a sea of fog filling the canyon like water Thursday.
It's caused by something called a "total cloud inversion." That happens when moist, cold air gets trapped in the canyon under a layer of warm air.
It doesn't happen very often, typically just once every few years. But yesterday's event is the second time it's happened in the last six weeks.
