This produces unstable conditions leading to showers. The common afternoon showers in tropical regions are also caused by this process. The Sun warms the ground during the day. By afternoon the moist, unstable air is being forced to rise giving rise to huge Cumulonimbus clouds and very heavy rain that arrives rapidly. This type of rain is caused by geography.
Air moving along the ground or over the sea, passes hills or mountains.
These force the air to rise in order to pass the obstruction. The rising air cools and, if moist, will form mist, clouds or rain on the side of the obstruction where the air is rising. As the air passes over the obstruction, it begins to descend. Descending air warms and will not cause rain. It is quite common where there is a prevailing wind, for one side of a mountain to be green and lush while the other side is drier.