Cumulus

Cumulus clouds often look like a piece of floating cotton with sharp outlines, a domed top, and a flat base.

There is usually a great deal of blue sky between each cumulus cloud.

Cumulus clouds that only show slight vertical growth are associated with fair weather. They are also called "fair weather cumulus".

Swelling Cumulus, or Cumulus Congestus

Once cumulus clouds begin to grow and resemble a head of cauliflower they are called cumulus congestus, swelling cumulus, or towering cumulus.

Most of the time these clouds are still separate, but sometimes they join together.

Showery precipitation falls from these clouds.

Cumulonimbus

Cumulonimbus clouds are thunderstorm clouds.

These clouds are huge clouds. Their bases may be no more thatn 2,000 feet above the earth's surface, while their tops extend over 39,000 feet higher into the atmosphere.

Cumulonimbus clouds may contain all forms of precipitation, and often produce thunder and lightning.