NZ went into lockdown for three days from midnight Tuesday, with Auckland and Coromandel expected to be in lockdown for seven days.
Here is what you need to know, and what you need to know across schools, health, shopping, exercise and going out.
Level four - dubbed the "eliminate" phase - means people must stay at home in their bubbles - travelling out only for essential personal movement.
Essential reasons for leaving the home briefly include:
• Physical exercise in your neighbourhood
• Visiting the supermarket, dairy or pharmacy
• Necessary medical care or getting a test
• People are instructed to stay at home in their bubble other than for essential personal movement
• Safe recreational activity is allowed in local area
• Travel is severely limited
• All gatherings are cancelled and all public venues are closed
• Businesses are closed except for essential services, such as supermarkets, pharmacies, clinics, petrol stations and lifeline utilities
• Educational facilities are closed
• Rationing of supplies and requisitioning of facilities is possible
• Reprioritisation of healthcare services
All New Zealand primary and secondary schools are expected to close for on-site learning.
The Ministry of Education said in a memo to schools last night that school hostels and residential special schools should send students home during lockdown. However, an exception will be made for students who cannot safely return home, such as international students.
Auckland Primary Principals' Association president Stephen Lethbridge said last night schools in the region were very well prepared for the transition back to home learning.
"We've learned a lot from each subsequent lockdown, and each time we do it a little better," he said.
That being said, it was going to be difficult for everyone, parents included, to adjust to level 4, he added.
New Zealanders won't be able to get a Covid jab for at least the next 48 hours while Government officials discuss how to ensure a safe process.
Prime Minister Jacinda Ardern last night said she wanted to ensure vaccinations could still take place in a safe environment.
"We will be considering whether drive-through vaccinations are the best options and looking at what other precautions could be put in place to ensure it was safe."
She said a further update on vaccinations could be expected in the next 24 hours.
Testing will be ramped up in a bid to detect any possible spread. Additional testing stations are being set up.
Meanwhile, healthcare professionals all have to wear Personal Protective Equipment to prevent any further spread.
Pregnant women can expect the same care from their midwives but non-critical appointments may be conducted via video.
Midwives union MERA's co-leader Caroline Canroy said midwives were "well seasoned" and "all geared up" to transition their work to alert level 4.
Royal New Zealand College of General Practitioners medical director Bryan Betty said most general practices would move into a predominantly virtual consultation model.
"Patients would be required to ring up prior to coming to see their GP, very similar to what we saw during last year's lockdown. Those patients who need to be seen in person will be," he said.
Most Auckland Council facilities will be temporarily closed to the public for the next seven days. They include libraries, pools, leisure centres, early childcare centres, community venues and playgrounds. Some public toilets will remain open. Auckland Council's public Wi-Fi at council libraries will be switched off and drinking fountains will also be unavailable under alert level 4.
The Government's advice under Alert Level 4 is to stay home and travel only when absolutely necessary.
Auckland Transport said public transport services would only be available for people working in essential services, for medical reasons, to access essential services including getting to the supermarket, pharmacy and Covid testing.
With schools being closed, school bus services will not operate.
People using public transport for essential travel must wear a mask and are being asked to use the AT mobile app to check the capacity on services and use the rear door when getting on and off a bus
Face masks are on sale in vending machines at public transport facilities across Auckland. The masks are in 42 machines at bus and rail stations and ferry wharves.
People are also asked to use QR codes on buses, trains and ferries, and to tag on/off with their AT HOP card.
Air New Zealand has made a number of changes to its services but will continue with its current schedule for the next 48 hours so customers can fly home.
Food and beverage service on domestic flights will, however, be suspended but water will be available.
Air New Zealand's lounges are closed. Valet parking will be closed to new bookings, but will stay open for 48 hours for customers to retrieve vehicles.
Customers with existing bookings for travel between August 17 and 24 can change their booking with change fees, with any fare difference waived through to August 31. Customers can do this via the airline's online booking tool. Those who have booked through a third party will need to contact their agent.
In addition customers witha ticket for a domestic flight scheduled to depart up till September 30 can opt in for credit and can do this via the airline's online booking tool.
People are urged not to panic-buy groceries. There were long queues last night swamping checkouts and shopping websites appeared to be crashing. Home delivery time slots booked out fast. Police will increase visibility at supermarkets to "provide both workers and the public with reassurance". Countdown spokeswoman Kiri Hannifin urged customers to "keep calm", wear a mask and use the contact tracing apps. "We're seeing extra demand for online shopping and remind everyone that all our stores are open and there is plenty of food so there's no need to buy more than you need."
New Zealand Fashion Week — scheduled to start next Monday — has been postponed. The event's founder and managing director Dame Pieter Stewart says it's disappointing for the designers, buyers, production teams, models and partners but health and safety comes first and they respect the Government's decision. Ticket holders can contact iTicket for refunds. Viva magazine — inside the Herald today — features Fashion Week. It was produced before the lockdown announcement.
New Zealand uses an alert level system as a way of managing and minimising the risk of Covid-19 in our country.
New Zealand's four-tier system - which was first introduced to Kiwis in March last year - is a way of helping people understand what risk is associated with current Covid-19 cases and what measures need to be followed.
The system starts with level 1 - dubbed the "prepare" stage - meaning the disease is contained in New Zealand but uncontrolled overseas.
Border restrictions remain in place including limiting who can travel here, health screening and testing in place for almost all arrivals and MIQ for anyone who is not travelling quarantine-free.
Under alert level 1, people are urged to stay home if they're sick and get tested if they have Covid-19 symptoms.
Face coverings must legally be worn on public transport, domestic flights and by taxi and ride-share drivers. Masks aren't compulsory for passengers but are strongly encouraged by health officials.
Under level 2, gatherings can not have more than 100 people - including weddings, civil union ceremonies, birthdays, funerals and tangihanga.
You can travel locally and to other regions that are at level 2 or lower, but need to do it in a safe way.
Those with cold, flu and Covid-19 symptoms, who are awaiting a test or need to self-isolate, should not travel.
Exercise and recreational activities are allowed and businesses can open under level 2 as well but must follow public health rules.
Health officials urge people to keep their distance from others when they're outside of their home - including two metres in public and retail stores, like supermarkets, and one metre in most other places, like workplaces and cafes.
Like level 1, face coverings must legally be worn on public transport, domestic flights and by taxi and ride-share drivers. Rise-share passengers are strongly encouraged by health officials to wear masks.
People are encouraged to use the Covid-19 tracer app and businesses must display the NZ Covid Tracer QR code poster.
People must stay within their household bubble whenever they are not at work or school.
Businesses that require close physical contact can't open - while those that do stay open must follow public health guidelines.
While people can travel within their local areas, such as going to the supermarket or getting exercise, travel between regions is heavily restricted.
Public venues - including libraries, museums, cinemas, food courts, gyms, pools, playgrounds and markets - must close.
Public transport continues to operate under level 3. Gatherings of up to 10 people can go ahead but only for weddings, civil union ceremonies, tangihanga and funerals.
People are encouraged to use the Covid-19 Tracer App to keep track of where they have been while businesses legally must display the NZ Covid Tracer QR code poster.
Like levels 1 and 2, face coverings must legally be worn on public transport, domestic flights and by taxi and ride-share drivers. Rise-share passengers are strongly encouraged by health officials to wear masks.
Much of the South Island is set to plunge below 0C tonight and tomorrow.