Mean temperatures at sea level decrease steadily southwards from 59° F in the far north to 54° about Cook Strait, then to 49° in the south. With increasing altitude, temperatures drop about 3° per 1,000 ft. January and February, with approximately the same mean temperature, are the warmest months of the year; July is the coldest. Highest temperatures are recorded east of the main ranges, where they rise to the nineties on a few afternoons in most summers, usually in association with a north-westerly Föhn wind. The extremes for New Zealand (measured in a standard thermometer screen) are 101° at Ashburton and – 3° at Ophir (Central Otago).
As is to be expected, there is a small annual range of temperature (difference between mean temperature of the warmest and coldest months). In Northland and in western districts of both Islands the annual range is about 15° F. For the remainder of the North Island, and east coast districts of the South Island, it is 17°–19. Further inland it exceeds 20° in places, reaching a maximum of 25° in Central Otago where there is an approach to a continental type of climate.