Cloud

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A **cloud** is water vapour in the atmosphere (sky) that has condensed into very small water droplets or ice crystals that appear in visible shapes or formations above the ground.

Water on the Earth evaporates (turns into an invisible gas) and rises up into the sky. Higher up where the air is colder, the water condenses: it changes from a gas to drops of water or crystals of ice. We see these drops of water as clouds. The drops fall back down to earth as rain, and then the water evaporates again. This is called the "water cycle".

The atmosphere always has some water vapour. Clouds form when the atmosphere can no longer hold all the invisible air vapor. Any more water vapor condenses into very small water drops.

* **Cirrus clouds** are high and thin.  The air is very cold at high levels, so these clouds are made of ice crystals instead of water droplets.  Cirrus clouds are sometimes called ''mares' tails* because they look like the tails of a horse.

* **Stratus clouds** are like flat sheets.  They may be low-level clouds (*stratus*), medium-level (*altostratus*), high-level (*cirrostratus*), or thick multi-level clouds that make rain or snow (*nimbostratus*).

* **Stratocumulus clouds** are in the form of rolls or ripples.  They may be low-level clouds (stratocumulus), medium-level (*altocumulus*), or high-level (*cirrocumulus*).

* **Cumulus clouds** are puffly and small when they first form.  They may grow into heap clouds that have moderate vertical extent (nothing added to the name), or become towering vertical clouds (*towering cumulus'').

* **Cumulonimbus clouds** are very large cumulus-type clouds that usually develop cirrus tops and sometimes other features that give them their own unique look.

The following is a summary of the main cloud types arranged by how high they form:

### High-Level clouds 
High clouds form from  in cold places,  in mild regions and  in the very hot tropics.  They are too high and thin to produce rain or snow.

High-level clouds include:

* Cirrus (Ci)
* Cirrocumulus (Cc)
* Cirrostratus (Cs)

### Medium-level clouds 
Middle clouds usually form at  in colder areas. However, they may form as high as  in the tropics where it's very warm all year.
* Stratocumulus (Sc)
* Stratus (St)

When very low stratus cloud touches the ground, it is called fog.

### Moderate-vertical clouds 
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These are clouds of medium thickness that can form anywhere from near ground level to as high as .  Medium-level cumulus does not have *alto* added to its name.  The tops of these clouds are usually not much higher than .  Vertical clouds often create rain and snow.  They are made mostly of water droplets, but when they push up through cold higher levels they may also have ice crystals.

Moderate-vertical clouds include:

* Cumulus (Cu)
* Nimbostratus (Ns)

### Towering-vertical clouds 
These clouds are very tall with tops usually higher than .  They can create heavy rain and snow showers.  Cumulonimbus, the biggest clouds of all, can also produce thunderstorms.  These clouds are mostly made of water droplets, but the tops of very large cumulonimbus clouds are often made mostly of ice crystals.

Towering-vertical clouds include:

* Towering cumulus (Tcu)
* Cumulonimbus (Cb)

## Gallery 

Image:PizBernina.jpg|Mountain peaks poking through ragged stratus clouds in the Swiss Alps.  
Image:Clouds from above.JPG|Cumulus cloud bow above the Pacific Ocean with low stratocumulus in the background. 

## As a sign 
In the Bible, clouds are often a sign of God's presence.

## References 
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## More reading
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