Cumulus

• This low cloud with a typical base of below 7,000 feet is
  a cumulus cloud. These clouds have distinct edges, are
  usually white, puffy with a popcorn like appearance.
  They have a noticeable vertical development. Cumulus
  clouds can be seen isolated as in this picture or grouped
  together is clusters. The cumulus cloud as all low clouds
  are most often composed of water droplets, but can can
  have ice crystals in colder climates.

                Stratus

• This stratus cloud is the lowest of the low clouds. They
  appear as a grey overcast deck, but can be scattered.
  Because the stratus cloud is low it too has a base below
  7,000 feet and is made of mostly water droplets. The
  individual stratus cloud has ill-defined edges compared to
  other low clouds.

                 Cirrus

• The high altitude cirrus cloud like the one shown here have
  bases above 18,000 feet. They are mostly made of ice
  crystals and appear wispy, thin; almost hair-like. Cirrus clouds
  generally occur in fair weather and point in the direction of air
  movement at their elevation.

                   Cumulonimbus

• The cumulonimbus cloud is the tallest of all clouds. They
  can span all cloud layers and extend to 60,000 feet. These
  clouds can produce lightning, thunder, heavy rains, strong
  winds, and tornadoes. Cumulonimbus clouds usually have
  large anvil-shaped tops because of the stronger winds at
  those higher levels of the atmosphere.