Ina, Here is a set of data that provides the average minimum temperatures for quite a few cities, including both Auckland and Wellington. http://niwa.co.nz/education-and-training/schools/… rtemp Indeed, as you'd expect, the minimum temperature each month is a bit lower in Wellington. Unfortunately, I could not find the lowest temperatures and presumably the person who put together the hardiness zone maps had such data. Nevertheless, I'd still expect Auckland, surrounded by so much influence from the sea to be subject to a smaller range of temperature and probably a higher values for the range of minimum temperatures (the basis for the hardiness definition). Andrew San Diego (in Zone 10 b - but it varies quite a lot over its hilly terrain and distance from the ocean)