New Zealand's Air Mass, Global Winds and Rain

1. Their main air mass is Maritime Tropical. 

2. New Zealand gets hit by prevailing south westerly winds. 

3. Orographic rainfall is the most common in New Zealand because on the west coast of the South Island the air masses are forced up and over the mountain ranges which makes the clouds cool and start to condense at the top of the mountains, this causes the leeward side of the mountain to be really dry.