You Won't Believe These Astounding Nature Photos Are Real

Mammatus Clouds

Mammatus clouds, or mammary clouds, earned their name because they resemble udders. These clouds often appear along with severe stormy weather or tornados; pilots avoid them due to turbulence. They are formed by cold air sinking in pockets, causing their unique shape as hot air rises in tandem. These clouds were first sighted in 1894. They may be pretty, but they're definitely bad news.

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