Shown in the photograph is a wall cloud with tail cloud.
Supercell - often associated with violent weather.
Clouds hang low over a valley at Graubunden, Switzerland.
Captured in this photo is a blazing sunset seen near Throckmorton, Texas.
Somewhere over the Rainbow
Stunning photo of a rainbow with a reflection over an Oklahoma Wheatfield.
Dolphins in the Sky
This photo, taken in Russia, seems to show wispy dolphins jumping in the clouds.
A thunderstorm anvil at sunset.
Turbulent gust front clouds.
Ominous Clouds Gather
Dark clouds gather over a campsite on the Tibetan Plateau. The photographer wrote of this photo, "Everybody was watching the monsoonal arcus cloud rolling over the camp. Suddenly, the weather changed. Rubbish was flying around and three men were hanging at the kitchen tent to keep it in place. This fascinating view presented itself shortly before the place turned into chaos."
A roll cloud, associated with thunderstorm downdrafts and strange sea winds, tumbles across the sky off the coast of Brazil. Roll clouds are rare and harmless, though ominous-looking.