Christchurch Mayor Lianne Dalziel has declared a state of emergency for Christchurch City, which includes Banks Peninsula, due to the impacts of Gita.
Meanwhile, Gita is poised to split in two when it hits the South Island later today.
The former tropical cyclone may be divided by the Southern Alps – sending the main storm over Banks Peninsula and a second, smaller storm towards the West Coast, the MetService says.
The split would not materially impact on the spread or strength of the storm, meteorologist Ciaran Doolin said.
Earlier today, Air New Zealand cancelled all flights in and of Wellington and four other centres as Cyclone Gita starts packing a punch with heavy winds and rain.
The airline has cancelled all Capital services from 2.45pm today through until midnight as well as those to and from Hokitika, Nelson (from 12pm), New Plymouth (from 11am) and Queenstown.
More than 57 schools and kindergartens are closed and State Highway 1 is shut north and south of Kaikoura because of heavy rain as Gita starts to make its presence known.
Gita is expected to make landfall across the country this afternoon and with it, forecasters predict powerful swells of up to 10m, rapidly rising streams and rivers, flooding and winds of up to 150km/h.
Authorities in the Marlborough Sounds have told campers to abandon their positions to be safe, and schools in the Buller region are closed. West Coast leaders will decide this morning whether to declare a state of emergency.
The remnants of the storm that battered Samoa, Tonga and southern Fiji is scheduled to arrive in New Zealand in the next 12 hours.
MetService meteorologist Nick Zachar said the system was northwest of New Zealand at 5am and was moving "pretty quickly" southeast towards the top of the South Island.
"We expect it to hit the Farewell Spit area and move across the top of the South Island from about 7 to 8pm."
The storm was re-classified as a former tropical cyclone about 1am.
READ MORE:
• Cyclone Gita: region by region forecast
• 10 ways to prepare for Gita
"But while it is no longer classified as a cyclone, it is still a strong storm.
"At the moment the winds are not too strong but we expect them to pick up to 130 to 140km/h, from Taranaki south to Canterbury, and reach 150km/h in Westland and the Canterbury high country."
One of the biggest concerns was 9-10m seas approaching the Cook Strait to the Taranaki coast.
"These waves won't reach the shore at that height, but there is still a risk of coastal inundation, especially in the Kapiti Coast area," Zachar said.
Westland Civil Defence public information manager Andy Thompson said the storm was yet to arrive in Greymouth but they were getting prepared.
"We are very much preparing for the worst, and absolutely hoping for the best."
West Coast mayors, public officials and emergency staff met last night and were meeting again this morning for an update on the storm and to decide if states of emergency needed to be declared.
Buildings partially damaged in former cyclone Fehi at the beginning of the month were a "major concern".
"On the West Coast the major concern is not so much the heavy rain but the strong winds and storm surges," Thompson said.
"That is what caused the most damage during Cyclone Ita in 2014, when we had winds of 140 to 160km/h.
"We expect the worst hit area to be Karamea, which is looking to be right in the eye of the storm."
Grey District mayor Tony Kokshoorn said the memories of Cyclone Ita were still fresh for many people.
"The gusts then ripped roofs off houses, and the gusts with Gita are predicted to be similar and hang around for 36 hours.
"Some buildings and trees are still being secured [after Fehi], and there are fears [Gita] will exacerbate those issues.
"We want everyone to be safe and secure all of their stuff."
Revington's Hotel, on Greymouth's main street, had its roof partially pulled off during Fehi and was now a safety hazard.
"The owners have secured it as much as they can, but it is in the main street so could be dangerous."
Another concern was the former rubbish dump near Cobden Beach, which had its side ripped out by a storm surge during Fehi, scattering tens of thousands of plastic bags along the coast.
Since then the council had begun securing the site by building a rock wall.
"It is much more secure than it was two weeks ago. We are also not expecting the storm surges to be as bad as with Fehi either."
Gita is tracking southeast towards New Zealand while transforming into an ex-tropical cyclone and would move southeast across central New Zealand today.
People are being advised to secure property and items that may be blown away by the severe gales expected.
For the North Island, coastal areas from Raglan to southern Wairarapa were most at risk. For the South Island, the risk of coastal inundation was greatest for Buller and North Canterbury northwards, MetService said.
Heavy rain warnings were in place for Nelson, Buller, Marlborough (including Kaikoura Coast), Wellington, Westland and the Canterbury high country.
Strong wind warnings were in place for Taranaki, Taihape, Whanganui, Nelson and Buller, Marlborough, Westland and Canterbury.
Yesterday, Associate Transport Minister Julie Anne Genter, Climate Change Minister James Shaw and Civil Defence Minister Kris Faafoi were updated on the progress of Gita at the MetService headquarters in Wellington.
West Coast Civil Defence had intended to make a call whether they would declare a state of emergency yesterday but had opted to make the decision this morning, authorities said.
It advised people not to travel during the storm, and closed all local schools.
The Nelson and Tasman Civil Defence (CD) warned the power of Gita will be similar to that of ex-cyclone Fehi, which battered and flooded several properties two weeks ago.
Those same properties were likely to be affected again.
The storm would also likely flood roads, making travel around the region difficult.
Winds of up to 140km/h had the potential to topple trees and make driving difficult.
Marlborough District Council communications manager Glyn Walters said they were concerned for trampers and campers who might be relying on tents but that the locals would be able to bunker down if they had sufficient supplies.
But many campsites in the region have reported being full, or having busier than normal bookings as freedom campers seek a populated safe haven.
"We are having more people come in because it is mainly the tourist trade now and they are running for cover," a Motueka Top 10 Holiday Park spokeswoman said.
A spokeswoman for Marahau Beach Camp, near Abel Tasman National Park, said only a few campers had left because they were worried about the storm, but most were trying to find accommodation in cabins or at backpackers.
Tourists on the West Coast were also reported to be exuding a "cruisey" attitude about the approaching storm.
"Everyone is cruisey and will worry about it tomorrow. We have to wait to see if it hits or not," a Greymouth Seaside Top 10 Holiday Park spokesman said.
Carters Beach Top 10 Holiday Park owner Chrissy Alfeld said they were focusing on keeping people informed and safe.
Meanwhile the Mountain Safety Council warned the storm was not to be underestimated, advising people to stay away from rivers and consider postponing outdoor activities.
People heading outdoors in the next 48 hours needed to be prepared to change their plans, chief executive Mike Daisley said.
"The right decision may be to postpone your trip until the weather settles down."
Heavy rain warnings
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
Area: Nelson and Buller
Valid: 14 hours from 7am to 9pm Tuesday
Forecast: Expect 150 to 200mm of rain to accumulate in Nelson west of Motueka, and 90 to 150mm elsewhere. Peak intensities of 20 to 30mm/hr possible.
Area: Marlborough including the Kaikoura Coast
Valid: 15 hours from 7am to 10pm Tuesday
Forecast: Expect 150 to 200mm of rain to accumulate about higher ground, and 90 to 140mm elsewhere. Peak intensities of 20 to 30mm/hr possible.
Area: Wellington and Kapiti Coast
Valid: 15 hours from 1am to 4pm Tuesday
Forecast: Expect 75 to 100mm of rain to accumulate. Peak intensities 20 to 30mm an hour during the morning. Lighter rain is expected from late Tuesday afternoon to midnight Tuesday.
Area: Canterbury Plains (excluding Christchurch) and High Country, the ranges of Westland
Valid: 27 hours from noon Tuesday to 3pm Wednesday
Forecast: Expect 150-200mm of rain to accumulate during this period about Canterbury High Country, and 90-120mm elsewhere. Peak intensities of 2030mm/hr possible about Canterbury High Country.
Strong wind warnings
Strong wind gusts could damage trees, powerlines and unsecured structures. Driving may be hazardous, especially for high-sided vehicles and motorcycles.
Area: Taranaki, Taihape, Whanganui
Valid: 10 hours from 3pm Tuesday to 1am Wednesday
Forecast: Severe gale north to northwest winds gusting 120km/h in exposed parts of North Taranaki, but damaging gusts of 140km/h in exposed parts of South Taranaki, Whanganui and Taihape.
Area: Manawatu, Kapiti-Horowhenua, Wellington and Wairarapa including the Tararua District
Valid: 8 hours from 7pm Tuesday to 3am Wednesday
Forecast: Severe gale north to northwest winds gusting 120km/h in exposed places, but 130km/h in Wellington on Tuesday evening.
Area: Nelson and Buller
Valid: 8 hours from 2pm to 10pm Tuesday
Forecast: Severe gale east to northeast winds with damaging gusts of 130-140 km/h in exposed places.
Area: Marlborough including the Kaikoura Coast
Valid: 12 hours from 3pm Tuesday to 3am Wednesday
Forecast: Severe gale southeasterlies gusting 120km/h or more in exposed places.
Area: Westland and the Canterbury High Country near the Alps
Valid: 13 hours from noon Tuesday to 1am Wednesday
Forecast: Severe gale southeast winds with damaging gusts of 150km/h possible in exposed places.
Area: Canterbury from Banks Peninsula northwards
Valid: 8 hours from 7pm Tuesday to 3am Wednesday
Forecast: Severe south to southeast gales gusting 120km/h in exposed places.
Today's weather
Whangarei: A few showers, turning to rain afternoon, easing evening. Northerlies becoming strong morning, easing evening. 28C high, 19C overnight.
Auckland: A few showers developing morning, then a period rain afternoon, easing evening. Northerlies becoming strong morning, easing evening. 28C high, 19C overnight.
Tauranga: Periods rain, more persistent in the evening. Northerlies becoming strong in the afternoon, easing overnight. 26C high, 20C overnight.
Hamilton: Cloudy, with a period of rain afternoon. Northerlies becoming strong morning, easing late. 28C high, 18C overnight.
Napier: Cloudy periods, chance evening shower. Northerlies becoming strong. 31C high, 20C overnight.
New Plymouth: Periods rain, easing evening. Northerlies rising to gale in the morning gusting 140 km/h. 26C high, 19C overnight.
Wellington: Rain, with heavy falls, especially in the morning. Southerlies, changing gale northerly gusting 130km/h this evening. 22C high, 14C overnight.
Nelson: Rain with heavy falls. Gale easterlies gusting 140km/h, changing northwest this evening. 22C high, 16C overnight.
Christchurch: Rain, with heavy falls from afternoon. Southeasterlies changing strong southwesterlies evening. 16C high, 11C overnight.
Dunedin: Periods of rain from late morning, with possible heavy falls from afternoon. Southerlies tending southeast late morning, then strengthening. 14C high, 11C overnight.
