Relief rainfall is a type of rainfall that occurs when moist air encounters mountains or hills, resulting in precipitation. It is also known as orographic rainfall. Relief rainfall is formed when the air cools as it rises over relief features in the landscape such as hills or mountains. As the air rises, it cools, condenses, and forms rain. The highest rainfall totals of over 1,600 mm per year occur in the mountain areas along the west coast. There is often a rain shadow effect whereby the leeward (downwind) slope receives a relatively small amount of rain. The following are the stages of relief rainfall:

1. Warm wet air is forced to rise over high land.
2. As the air rises, it cools and condenses. Clouds form, and precipitation occurs.
3. The drier air descends.
4. As the air descends, it warms, meaning it can carry water moisture, so there is little rain on this side of the mountain. This area is known as a rain shadow.

Relief rainfall is a phenomenon that occurs in various regions worldwide, particularly in areas with mountainous or hilly terrain. It plays a big role in determining how much rain falls in certain areas and affects the local climate.