偏西風の影響を強く受けるため、ニュージーランド南島、サザン・アルプスの西側斜面は、年間降水量10,000mmを越す。一方、風下側となる山脈東側の盆地や海岸の平野では年降水量600mm以下(東京は1500mm)で乾燥した草原が広がる。
そのため東岸のカンタベリー平野では、潅漑用の水路や、巨大なスプリンクラーが随所に見られる。
The southern alps give Canterbury a climate of greater extremes than most other parts of New Zealand.
Of the country’s main cities, Christchurch has the least rainfall and the greatest range of temperatures.
The mountains lie at an angle to the prevailing westerly air flow. These westerlies lose their moisture when they rise to cross the alps. On the eastern ranges and the plains, rainfall is much less.
Rainfall on the plains comes from the south and east, when depressions off the east coast push southerly flows over Canterbury.
Christchurch has an average annual rainfall of 648 mm (roughly half that of Auckland and Wellington).
