Rain omens are superstitions that people have believed in for centuries. They are signs of rain that people look for in the sky or in nature to predict when it will rain. The most common rain omen is the presence of CLOUDS, which is a 6-letter word that can be found in a crossword puzzle. CLOUDS are made up of tiny water droplets that form when warm air rises and cools, causing condensation. When the droplets become too heavy, they fall as rain.