These are probably some of the coolest clouds you can ever see. Comprised mostly of ice, they form under the anvil of supercell thunderstorms and oftentimes are a sign of severe weather to come. These particular clouds were underneath a storm that was approaching Lamar, Colorado last Thursday, June 11, 2015. The storm brought powerful winds and hail 2 1/2 inches in diameter.
![Mammatus clouds bubble underneath a supercell thunderstorm. (© Tony’s Takes)](http://lh3.googleusercontent.com/-Daym0CSXXmA/VX2Emk8RzBI/AAAAAAAANRo/mm-PYxZVS5Y/s710/2015-06-11%2B15-22-33%2B-%2B0245.jpg)