Rainfall is classified into how many types?

On the basis of origin, rainfall may be classified into three main types – the Convectional, Orographic or relief and the Cyclonic or Frontal.
The air on being heated becomes light and rises up in convection currents.
As it rises, it expands and loses heat and consequently, condensation takes place and cumulus clouds are formed.
Convectional precipitation is heavy but of short duration, highly localised and is associated with a minimum amount of cloudiness.
It occurs mainly during summer and is common over equatorial doldrums in the Congo basin, the Amazon basin and the islands of south-east Asia.

• Orographic Rainfall:
This type of precipitation occurs when warm, humid air strikes an Orographic barrier (a mountain range) head-on.
Due to the initial momentum, the air is forced to rise. As the moisture laden air gains height, condensation sets in, and soon saturation point is reached.
The surplus moisture falls down as Orographic rainfall along the windward slopes.
 

Frontal or Cyclonic Rainfall
When two air masses with different temperatures meet, turbulent conditions are produced.
Along the front convection takes place and causes precipitation. 
For instance, in north-west Europe, cold continental air and warm oceanic air converge to produce heavy rainfall in adjacent areas.
Cyclonic Rainfall is convectional rainfall on a large scale.
The precipitation in a tropical cyclone is of convectional type while that in a temperate cyclone is because of frontal activity.