The distribution of New Zealand’s ample rainfall is greatly affected by the mountains. In general, the east is drier and the west is wetter. The mean annual rainfall varies from less than 500 millimetres in Central Otago to over 6,000 millimetres at Milford Sound (in the south-west South Island). Most areas receive 600–1,500 millimetres per year, but large areas of both islands receive over 2,500 millimetres.

New Zealand has small areas of higher rainfall, which can’t be seen on a map of this scale, such as a narrow band on the Southern Alps that gets 10,000 millimetres of rain per year. The highest recorded annual rainfall was over 18,000 millimetres, measured at Cropp River on the West Coast.