Weather and Climate

The Matukituki Valley is situated immediately to the east of the main divide of the Soputhern Alps. It is thus subjected to West Coast storms, and the prevailing westerly winds bringing moist air from the Southern Ocean, as well as the dry semi-arid conditions that persist in the Southern Alps rainshadow. This semi-arid climate dominates the Wanaka – Hawea - Central Otago area and also the Upper Waitaki basin. The inter-montane character of the Upper Waitaki basin ensures some sub-continental aspects of climate in contrast to the temperate-oceanic climate of New Zealand as a whole. In general the Basin is dry in the south and east and moist in the north and west, with hot summers and cold winters.

There is a precipitation gradient of rainfall from about 450 mm/yr in the south-east to ~ 1000 mm/yr in the north-west. A distinctive factor in rainfall is the wide variability and seasonality. Indeed annual or monthly records are a poor guide because of the variability from year to year. On average, snow falls just 6-12 days each year, with the months from May to September having more than one day of snow per month.
There may be considerable variation in snow accumulation patterns from site to site and from year to year.

The continental character of the Basin is reflected in annual, diurnal and extreme ranges in temperature. The nocturnal radiation-cooling characteristic of inter-montane basins and the influx of cold air by downslope draining from neighbouring mountains leads to the likelihood
of low night temperatures at any time of the year and accounts for large daily temperature ranges. There are lower winter temperatures and higher summer temperatures than in lowland regions for example.

The Upper Waitaki Basin enjoys high sunshine hours, averaging 2000-3000 hours/year. High sunshine is the result of low cloud cover.
The north-west cloud bank stops to the west of the Basin, and the mountains to the east prevent the ingress of cloud banks from the seas.

Degree-day values suggest that plant growth is extremely retarded between May-September and there is no season
which can be called frost free.