National Weather Service United States Department of Commerce

Introduction to Clouds

We see clouds almost daily. But clouds are complicated and varied. In fact, the presence of a generic cloud means almost nothing without more details.

Clouds can grow very tall or appear flat as a pancake. They are typically white in color but can also be different shades of grey or brilliant yellow, orange or red. They can weigh tens of millions of tons yet float in the atmosphere.

Clouds can be harbingers of good weather or bad. Their absence can be a good thing after a flooding rain or a bad thing during a drought.

They provide relief from the heat of direct sunlight but also trap warmth, leading to higher temperatures.

Precipitation from clouds helps crops to grow, but can make driving more dangerous due to reduced visibility.

They come in infinite shapes and sizes yet we often recognize more familiar objects or animals.

Cumulonimbus cloud seen from 38,000 feet.

Clouds can be carried along by winds of up to 150 mph (240 km/h) or can remain stationary while the wind passes through them.

They can form behind high flying aircraft or can dissipate as a plane flies through them. They are not confined to earth but are found on other planets as well.

What are clouds? They are the visible aggregate of minute particles of water and/or ice which form when water vapor condenses. Learn about clouds and how they form to become "Cloudwise".