(A) OROGRAPHIC RAINFALL;
This form of rainfall is experienced whenever moisture-laden air is forced to ascend a mountain barrier when warm moist air carries tremendous moisture.
The air, upon reaching the land surface is compelled to move to the upper atmosphere particularly when it come in contact with a mountain barrier. As it ascends higher into the upper atmosphere, it cools by expansion. Coupled with decrease in the atmospheric pressure the air is further cooled so that it becomes wholly saturated. Condensation. at the point sets in, thereby forming clouds and finally rain.

(B) CONVENTIONAL RAINFALL;
It is very common in regions of great temperatures (tropics) and occurs in the day time. When the earth's surface is heated, the air expands and becomes lighter. After a long period of intensive heating, the air will be forced to rise thus carrying into the upper atmosphere water vapour.
At the
upper atmosphere, the water vapour condenses into cumulonimbus cloud and later turns into water droplets. Where the droplets become quite heavy for upward movement, it fails back as rainfall.
Thunder and lightening accompany rainfall.