Why Rain Clouds Get Dark: Water & Light

This podcast explains why rain clouds appear dark or gray, while other clouds often look white. It highlights that clouds are formed from countless microscopic water droplets and ice crystals.

The primary reason for the dark appearance of rain clouds is their thickness and density. While thin clouds allow sunlight to pass through easily, scattering all colors equally to appear white, thick storm clouds contain so many water droplets that they block or scatter most of the light. This means less light penetrates through the cloud to reach the observer's eyes from below, making the underside of the cloud look dark or gray. As water droplets grow larger just before falling as rain, they also become more efficient at absorbing light rather than scattering it, further contributing to the dark appearance. Therefore, a dark cloud is often a strong indicator that rain or a severe storm is likely.