From Cape Reinga in the north to Bluff in the south, New Zealand is about 870 miles (1400 km) long, so there's a lot of climatic variation. Northern Northland is subtropical, while southern Southland is cool and temperate, and in between the two extremes are areas of high alpine conditions as well as relatively warm coastal areas.
January (along with February) is the hottest time of year throughout the country, with highs of around 77° F (25° C) in Northland, Auckland, the Coromandel, other parts of the upper North Island, and even some parts of the South Island, such as the area around Nelson, parts of Canterbury, and parts of Central Otago. Being an island nation, the temperatures don't tend to get extremely high (nothing like neighboring Australia, for instance), but it's not unusual for some of the abovementioned places to get above 86° F (30° C) at times in the summer, sometimes for days at a stretch.
At the same time, parts of the country can be quite cool in the summer, with unseasonal (but not necessarily unusual) snowfall in alpine areas. The average summer high in Queenstown, in the south of the South Island and surrounded by mountains, is a cooler 71° F (22° C).
In general, New Zealand is quite a wet country, and rain should be expected at any time. But, the summer is normally the driest time of year. Water restrictions aren't uncommon in some parts of the country, which may not see significant rain for six weeks or two months over summer. This means conditions in January are good for spending time at the beach, or for hiking.
Be aware that forest fires are an increasing occurrence in New Zealand in the summer, and while these haven't (yet) reached the severity of those that happen in Australia or parts of the USA, it's important to be aware of this risk when out and about in nature in the dry, hot summer. Don't do something that could accidentally spark a fire, like throw a cigarette butt on the ground.
Crowds and Costs
January is peak tourism season in New Zealand. Primary and secondary schools take long summer holidays between mid-late December and late January/early February. New Zealand families travel around their own country, or spend time at their local beaches, lakes, rivers, and other attractions.
Popular camping areas can book out months in advance in January, as locals often have a favorite spot that they return to every year. 'Freedom camping' is frowned upon in many parts of New Zealand, and legislated against in some, so if you plan to camp in January, make sure you've done your homework about where is available and accessible.
If you plan to cross the Cook Strait between Wellington and Picton on the Interislander Ferry in January, make sure to book your tickets well ahead of time. Again, locals make this trip and book tickets well in advance, plus there's an influx of overseas tourists at this time.
Aside from domestic tourists, a lot of international tourists come to New Zealand in January. If you're from North America or Europe, visiting New Zealand in January is a great way to escape your winter.
In general, accommodation prices are higher in January, and you may have to pay more for domestic flights too, as popular routes are in demand.
Where to Go
There's no bad place to go in New Zealand in January. If you want to spend time at the beach, you'll be spoilt for choice. Northland and the Coromandel Peninsula have some of the best beaches in the country, but they also get the busiest in January. For a less busy beach experience, drive down the east coast of the North Island and see what you come across (the west coast of both islands tends to be less suitable for swimming because of wilder seas with stronger currents and heavier surf).
There's also no shortage of amazing day or multi-day hikes to try. The most popular trails (such as the Department of Conservation's 10 'Great Walks') can get pretty busy in January, with accommodation en route (DOC huts and campsites) booking up. Unless you have your heart set on doing them, avoid the Tongariro Alpine Crossing or the Abel Tasman Coast Track in January, as these get a lot of visitors, potentially straining the infrastructure and environment. There are plenty of other trails throughout the country that don't have the same volume of visitors.
While you won't be able to ski in January (ski season runs from June to early October), this is a good time to make a road trip to see the mountains, especially in the south. Road conditions are better than they are in winter (that is, not icy or covered in snow), and the mountains look beautiful in the sun! Aoraki Mt. Cook is New Zealand's highest mountain, and easily accessible from Christchurch.
What to Do
January is an ideal time to hit the beach, whether that's just lazing on the sand, swimming, or trying water sports like surfing, stand-up paddling boarding, or kayaking. Surf Life Saving patrols have a presence on many popular beaches, daily throughout the school holidays and just on weekends thereafter through the summer. Swim between the flags if there are flags present.
As mentioned above, January is also a good time to go hiking. Although conditions can be hot and sunny, you're less likely to encounter problematic rain. New Zealanders themselves love to hike, so wherever you go in the country, you won't be far from a trail.
City sightseeing and cultural activities can also be enjoyed in January, from the museums and galleries of Auckland, Wellington, and Christchurch, to the important historical sites of the Bay of Islands and the amazing natural features of Rotorua and Taupo.
World Buskers Festival, Christchurch. This late-January festival brings together local and international street performers, musicians, magicians, jugglers and more, for fun events over a couple of weeks.
ASB Classic Tennis, Auckland. Watch some of the biggest stars in tennis play over two weeks in January.
Traveling to New Zealand in January? Check out these great itineraries
Highlights of New Zealand - 10 Days. This action-packed itinerary dives into New Zealand's South and North Islands for a wide variety of landscapes and attractions.
New Zealand North Island Self-Drive and Cycling Tour - 10 Days. This self-drive itinerary covers the highlights of New Zealand's North Island, from Auckland to Wellington. Along the way, park your car and switch to a mountain bike to ride unique cycling trails.
South Island Tour: Christchurch, Akaroa, and Hanmer Springs - 5 Days. Enjoy the outdoors of New Zealand's South Island on this quick, five-day trip that takes in some of the best sights and activities in Canterbury.