New Zealand’s climate is influenced strongly by geographic factors, including:
- its location between the latitudes of 40 and 50 degrees with prevailing westerly winds (known as the ‘roaring forties’)
- a large area of surrounding ocean
- mountain chains modifying weather systems that move eastward
- tropical weather patterns (ie storms that begin as tropical cyclones elsewhere and redevelop in the region, bringing warm moisture-laden tropical air that interacts with colder polar air).
Because of these factors, New Zealand’s weather is more variable than that of larger, continental countries.
The average rainfall in most urban areas is between 600 millimetres and 1,500 millimetres a year (Ministry for the Environment, 2007). However, in the mountain ranges, annual rainfall often exceeds 4,000 millimetres a year (Ministry for the Environment, 2007).
Regions exposed to weather from the west and southwest experience a lot of precipitation – rain falls in these areas on about half of the days of the year. The rest of the country experiences much lower rainfall, particularly in eastern areas.
For more information see: Atmosphere and climate chapter.