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Since water vapor is white, what gives storm clouds their grey appearance?
Thank you.
Regards, Laura M.
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An excellent question for sure, we could also wonder why the clouds appear pink or orange or sometimes green, but we'll save that for another day.
A lot of the time when we look at clouds, they just look white. Water Vapor is not white actually, water drops or ice crystals don't reflect or scatter only one color, they scatter all colors which makes them look white. Light is reflected off of the droplets in the cloud to make it look white to you.
When clouds grow thicker, often times, ahead of storm, the sunlight cannot make its way through the cloud, so you see a gray cloud. Also, larger raindrops absorb more of the light at the bottom of those clouds which means less light will be relfected.
During a thunderstorm, you might see a large cumulonimbus cloud but it might be white on the top and gray at the bottom. This could just be the sun is setting and hitting the upper part of the cloud, where the light is then reflected and it looks white to you.
When clouds are thinner there are less cloud layers to shadow or block the sunlight, so thinner clouds can look whiter.
Answered by KSL Meteorologist Dina Freedman
