Snow or rain is precipitation in the form of liquid water droplets greater than 0.5 mm or smaller, but very few droplets that fall on the edge of the rain area. Dense precipitation droplets smaller than 0.5 mm in diameter is called Drizzle. Sometimes the clouds is striking how many fine particles of dust or sand raised from the ground to dust or sand storms in the dry areas. These particles fall along with the rain giving it a reddish to yellowish color (muddy or bloody raining and our regions). Rainfall variable intensity of cumulonimbus called downpour. Cloudy elements are tiny water droplets and / or ice crystals that formed by condensation or sublimation of water vapor. Precipitation elements (rain drops, crystals, flakes) are much larger and caused other physical processes that are not necessarily following the occurrence of cloudy elements. Stormwater elements usually occur in three ways:

predestilacijom with refrigerated vapor droplets to ice crystals, and these droplets and crystals has in the clouds where the temperature is below freezing

predestilacijom steam from hot to cold droplets in the clouds where the temperature is higher than the freezing point

coalescence, merging smaller droplets with larger ones, which are falling faster and on its way to collect slower smaller droplets.

The first form is important in temperate latitudes and polar regions, where each rain begins as snow in height. If the layer of air between the cloud and the ground warm enough, the snow melts and rains. Another way comes primarily in tropical and equatorial, where the air is warm to the high altitude and the third way everywhere. Theory of rain enabled the production of artificial rain clouds infilling particles of silver iodide, dry ice, tiny droplets of water. Hail is based on the same principle: infilling of clouds allows the creation of a large number of small rainfall elements instead of a small number of large and damaging.

Basically meteorologists are two types of rain: "cold rain" and "warm rain".

About 80% of the rain cold rain, the other 20% of the warm rain, and the difference is in the process of formation of raindrops.

When the sun heats the Earth's surface evaporates the water. Heated air and gaseous water vapor rising from the ground. What's hotter air to more water molecules can accommodate. In addition to water vapor is everywhere in the air are invisible and small aerosol particles. They are so small and light that they are airborne, although not in a gaseous state. The higher the altitude the air is more cool. What is an air cooler that fewer molecules of water vapor can contain - for scientists to say that the cold air before enough of. Only when the air is saturated with water vapor can form clouds, while excessive water vapor on aerosol particles into fine droplets. The droplets are thin as hairs and so light that they can hold up.

Condensing steam again teaches energy that was needed the sun to evaporate the water. Thus, the surrounding air is still hot and could continue to rise in the air. On his way to the height of the cloud droplets accidentally collide and merge.

On cold altitudes at about -20 ° C is still ongoing but very sub cooled cloud droplets partially frozen in ice crystals. They continue to grow so that the air consuming water vapor. When heavy enough start falling down still more expensive cloud droplets. Crystals are zgrudavaju so the sole grain pellets. As soon as you cross the boundary temperature of 0 ° C again to melt and fall to the ground as a cold rain. Rain, then, is a "cold" because of its splash before that were frozen beans salted or city.

Warm rain first occurs in the same way as the cold rain, but cloud droplets do not freeze it just collide until they become so large and heavy that they start to fall. Since during this process again and again the cloud droplets evaporate, this process usually takes longer than the process of the formation of cold rain.

In some cultures have developed equipment to combat rain like an umbrella or a raincoat. In tropical areas, people do not like to leave the house during rainy precipitation because the rain is most commonly associated with the storm.

Generally, rainfall is slightly below pH 6, due to absorption of atmospheric carbon dioxide, which in turns drops into smaller amounts of carbon acids. Rain pH below 5.6 is considered acidic rain.