Bioclimatic zones are broad zones of vegetation that correspond to mean annual temperatures at different latitudes and altitudes. This diagram shows five bioclimatic zones in the New Zealand region. Warm-temperate vegetation grows at low altitudes in the north. Cool-temperate vegetation is only found on mountain tops in northern New Zealand, but extends to low altitudes in the southern South Island and Stewart Island. Subalpine and alpine vegetation grows on the highest mountains and ranges of the North Island and extends to low altitudes on the subantarctic islands (at latitudes 50°–54°30′ south). The nival zone (where snow lies year round) occurs at altitudes above 2,000 metres in much of the Southern Alps (at 43°–44° 30′ south).