New Zealand has a temperate climate in the south island and sub-tropical climate in the North Island and the nature of the terrain, the prevailing winds and the length of the country lead to sharp regional contrasts. Maximum daytime temperatures sometimes exceed 30°C and only fall below 0°C in the elevated inland regions. Generally speaking, rainfall and humidity is higher in the west than the east of the country due to the north-south orientation of the mountain ranges and the prevailing westerly/north westerly winds.
Part situated in the Roaring Forties, unsheltered areas of the country can get a bit breezy, especially in the centre, through Cook Strait and around Wellington. The winds seem to be stronger around the equinoxes.
In the winter, southerly gales can be severe but they also bring snow to the ski-fields and are usually followed by calm clear days.
New Zealand is one of the most difficult countries in the world in which to forecast the weather. Although the weather is changeable, there is certainly more sunshine and warm temperate temperatures to enjoy in summer. It is not uncommon, especially on the South Island, to experience four seasons in one day.
New Zealand is a small country surrounded by ocean. A complicating, but often beneficial factor on the day to day weather, is the steep mountain range running down the spine of New Zealand orientated in a southwest-northeast direction. These mountains often shelter eastern parts of the country from an onslaught of westerly winds and rain.
The weather is mostly influenced by fast moving weather systems in the strong westerly winds, which are often referred to as the roaring forties, that predominate over southern parts of the country and seas to the south. There tends to be a seven day cycle associated with these westerlies as a cold front sweeps over the country associated with a couple of days rain, somewhere over the country. Often though these westerlies are disrupted by large high pressure systems or by storm systems.
During the summer and early autumn months from about December to April, the westerlies tend to move south giving more settled weather. Always be prepared for a change though. Also, during this time, random weather systems from the tropics can make their presence felt, mainly over the North Island, with a period of warm wet windy weather.
In the Winter, May to August, the weather tends to be more changeable. Cold fronts often bring a period of rain to western areas followed by a cold wind from the south bringing snow to the mountains and sometimes to near sea level over eastern parts of the South Island. When the weather turns cold and wet in the east, to the west of the mountains it will be fantastic. At this time of the year it is not uncommon for high pressure systems and clear skies to park over the whole country for long periods bringing crisp frosty nights and mornings followed by cool sunny days.
In spring, from August to November, the westerly winds are typically at their strongest – these are called the equinoctial westerlies. It tends to rain more in western areas, and especially on the South Island, at this time, while in the east, warm dry winds can give great cycling weather. Once again though, a cold front and its accompanying south winds can give you a taste of winter at any stage.
The Metservice has weather forecasts for five days in advance.