Wind and Rainfall.
The climate of New Zealand is clearly influenced by its latitude, shape, and geographical isolation resulting in a maritime style climate where the weather can frequently and rapidly change without warning.
The mountain chains running up the length of the South Island and through the North Island from Wellington to the Bay of Plenty place a barrier in front of the westerly winds that prevail across New Zealand in most seasons. This barrier results in very contrasting climatic conditions on the either side of these ranges.
In the South Island, warm moisture laden westerly winds originating from the Tasman Sea strike the west coast first. Reaching the mountain ranges, called the Southern Alps, they are swept upwards and rapidly cool. This causes the moisture to condense and and fall, equating to a much higher rainfall on the western side of the ranges. The winds, having now lost their moisture sweep over the Southern Alps and down across the plains on the eastern side. They gather speed and heat as they career towards the Pacific Ocean on the east coast, resulting in a very, hot, dry and fierce wind.
In the North Island, a barrier such as the Southern Alps does not really exist throughout. This leads to a much more evenly distributed rainfall throughout the year, with maybe an exception in the volcanic plateau, keeping the countryside well irrigated.
During severe winters in the South Island, inland Canterbury and Otago may receive vast amounts of snow, as well as exposed coastal areas on the eastern seaboard. Other than this, snowfall mainly occurs on the higher peaks of the Southern Alps and on the volcanic plateau in the central North Island all year round the year. In the far north snow is virtually never seen, and only falls occasionally on the west coast of the south island.
Temperature.
The South Island, being nearer the Antarctic, has an average temperature a little lower than the North Island. January and February tend to be the warmest months because it is the height of the summer season. This is certainly the best time to be outdoors in New Zealand, and it provides the longest stretches of fine weather. The months of June, July and August are the coldest months and best avoided because it is in the midst of winter. Most places will barely reach 10 - 12 degrees celcius, and in the south nearly all mornings begin with a frost.
However, the northern portion of the North Island has weather conditions similar to the tropics. The temperatures there stay relatively warm all year round, with fine settled weather a dominant feature. These features encourage outdoor activies all year round, and there are always plenty of tourists taking advantage of the miltitude of events on offer.
The weather in New Zealand follows a regular cycle throughout the year, but the time it takes for the weather to change is very inconsistant. The usual pattern for New Zealand weather is a high pressure system followed by a low pressure front, both sweeping over the country from the south west to the north east, following the mountain ranges.
The high pressure system usually consists of fine weather, light winds and warmer temperatures. It normally takes a high pressure system three to seven days to pass over the whole of the country. A low pressure front however frequently consists of rain, strong biting winds and colder temperatures.
Reading the weather in the bush yourself is an integral part of your survival. The north westerly conditions often fortell that bad weather is on the way. While the weather maybe settled at that moment, these conditions often forewarn a storm is brewing in the south. The cold southerly change that will bring rain, possibly snow and cooler temperatures is very unpredicatable and will often hit southern New Zealand before it os even forecast. These cold spells can last any length of time, but usually only a few days. Following these cold spells, settled weather should arrive again for a period of time.
The weather in New Zealand due to its unpredictability can only be forcast accurately for a couple of days in advance. Therefore it is vital for you to be aware that the weather can change rapidly in thebush, and if in doubt it is best to wait in a safe place. Pushing on in dubious weather is one of the most frequent causes of disater. One must also remember that the weather in New Zealand is much more severe in exposed places such as alpine territory, river valleys and open peaks. It is here you need to be extra careful, and if a storm does set in, find safe place to set up camp and sit it out.
