How Rains,Lightening and Thundering occurs?

                                       RAIN, LIGHTENING AND THUNDERING

Rains:

Water evaporates from earth and rises as water vapour above the Earth.

The atmosphere gets cooler as you go higher - by roughly one degree centigrade cooler for every 100m of altitude in dry air - so as the warm air rises it becomes cooled again by the colder air around it.

Eventually the air reaches a height where the temperature forces the water vapour in the warm air to start condensing. This is called the condensation point, and is where the clouds begin to form. The typical cloud formed this way is called a cumulus cloud, or a cumulonimbus cloud when it has a grey bottom and 'looks like rain'.

Lightening:

Water condenses in cloud and charge separation occurs within it. Positive charge accumulates at top and negative charge accumulates at bottom part of cloud.

In the world of electricity, opposites attract and insulators inhibit. As positive and negative charges begin to separate within the cloud, an electric field is generated between its top and base. Further separation of these charges into pools of positive and negative regions results in a strengthening of the electric field.

However, the atmosphere is a very good insulator that inhibits electric flow, so a TREMENDOUS amount of charge has to build up before lightning can occur. When that charge threshold is reached, the strength of the electric field overpowers the atmosphere's insulating properties, and lightning results.

As bottom part of the cloud stores negative charge so earth acts as positive body surface and this causes light reaches earth to balance the atmosphere.

Thunders:

Thunder is created by a rapid expansion of air. Think of a balloon popping. There is a sudden release of noise due to the rapid expansion of air. When lightning moves through the air it increases the temperature of the air dramatically in a very short period of time. The air then cools rapidly. This rapid expansion and contraction of the air gives off the sound waves that is heard from the lightning.

We can see after lightening it takes some time to hear thunder it’s a sound, as we studied in our primary education light travels more speed than sound.

References:
             http://www.srh.noaa.gov/jetstream/lightning/lightning.htm
             http://www.geography-site.co.uk/pages/physical/climate/why%20does%20it%20rain.html
             http://scijinks.jpl.nasa.gov/lightning/
             http://www.theweatherprediction.com/kid_weather_questions/lightning_thunder.html