Sky and clouds

Snowfall

Snowfall

Sunset colors

Sunset colors

After the storm

After the storm

Clouds at night

Clouds at night

Big clouds

Big clouds

Cloudy sky

Cloudy sky

Cloudy sky

Cloudy sky

Thunderstorm

Thunderstorm

Whipping wind

Whipping wind

Lightning

Lightning

Clouds are formed by microscopic drops of water or by small ice crystals. The size of the droplets generally range from a couple of microns to 100 microns: this is the limit beyond which cloud drops become rain drops. Cloud formation is apparently a very simple process, caused by the condensation of atmospheric humidity into drops of water, but in actual fact it is a more complex phenomenon, in which different factors and mechanisms are involved. All the processes however are based on the ascent of a mass of humid air and its successive cooling up to dew point. A cloud is the visible expression of this process. The condensation process is favoured if particles and impurities are present that can act as condensation nuclei on which the droplets can deposit.