With ocean in every direction it is no surprise that New Zealand has a maritime climate, warm in the summer months, December to March, and never truly cold, even in winter. Weather patterns are strongly affected by prevailing westerlies, which suck up moisture from the Tasman Sea and dump it on the western side of both islands.
The South Island gets the lion’s share, with the West Coast and Fiordland ranking among the world’s wettest places, worth bearing in mind when deciding the best time to visit. Mountain ranges running the length of both islands cast long rain shadows eastward, making those locations considerably drier. The south is a few degrees cooler than elsewhere, and subtropical Auckland and Northland are appreciably more humid.
In the North Island, warm, damp summers fade imperceptibly into cool, wet winters, while the further south you travel the more the weather divides the year into four distinct seasons.
Most people visit New Zealand in the summer, but it is a viable destination at any time provided you pick your destinations. From December to March you’ll find everything open, though often busy with holidaying Kiwis from Christmas to mid-January.
In general, you’re better off joining the bulk of foreign visitors during the shoulder seasons – October, November and April – as sights and attractions are quieter, and accommodation easier to come by.
Winter (May–Sept) is the wettest, coldest and consequently least popular time, unless you are enamoured of winter sports, in which case it’s fabulous. The switch to prevailing southerly winds tends to bring periods of crisp, dry and cloudless weather to the West Coast and heavy snowfalls to the Southern Alps and Central North Island, allowing for some of the most varied and least-populated skiing and snowboarding in the world.