This image was taken just after sunset July 21st 2013.

The sun had just set and was casting anti-crepuscular rays off of the beautifully structured cumulonimbus cloud.  A nearly full moon made for a beautiful view.

CUMULONIMBUS clouds are the massive, towering thunderheads so common in the summer. When the puffy, fair-weather cumulus clouds come together, they combine and begin to build upward. Violent up-and-down wind currents within the clouds develop, causing the top to boil higher and higher. When the cloud moves into the higher atmosphere an anvil-shaped top of ice crystals develops. This icy cirrus top stretches out flat and points the wind direction. Lightning, heavy rains, and often hail are created as the water clusters within the cloud are tossed up and down. This cloud may cover many square miles.