What is a relief rainfall?

Relief rain usually takes place around coastal areas where a fleet of hills runs along to the coast. When wet onshore wind from the sea meet a mountain, hill and barrier, it is forced to rise along the slope and cools. When the air temperature falls to its dew point, water vapor condenses to form clouds. When the clouds can no longer hold the water droplets, relief rain begins to fall on the windward slope of the mountain. On the leeward slope, air sinks, it is warmed and further dried by compression. Therefore, the leeward slope is known as rain shadow.