I would love to have seen this
magnificent rainbow cloud, but it was spotted over Costa Rica, a place I've never been.
The cloud formation, called a pileus or cap cloud, forms when a building thunderstorm rises quickly in height. As it does this, the air above it cools and condenses into a cloud that looks a bit like a hat sitting on another cloud. The rainbow was the result of ice crystals refracting sunlight.
(The Internet was abuzz with people who'd decided it meant the end of the world, rather than a thunderstorm, was coming. Sigh)
