Cold temperatures, icy winds and snow is expected in the coming days as a nasty low moves over the country bringing undesirable conditions to most areas.
MetService was keeping its eye on a cold outbreak as southerly changes pushed up from the Southern Ocean bringing turbulent weather with it, MetService meteorologist Andy Best said.
"The trough moves over central New Zealand by midday Monday, then over the upper North Island Monday evening. Strong, cold southerly winds will follow in the wake of the trough."
The cold air would spread over the east of the South Island today.
Paired with moist air, parts of the south including Southland, parts of Fiordland, Otago, Canterbury and Marlborough will likely get a drop of snow.
In the south, a strong wind watch was in place around Christchurch, especially about Banks Peninsula.
In the north, the same watch was in place for Wairarapa, south of Martinborough.
A wet, white, and windy time across NZ over the next two days 🌨️ 🌧️ 🌬️
— NIWA Weather (@NiwaWeather) September 1, 2018
Our high-resolution weather model captures a southerly change charging up the South Island tonight and into the lower North Island tomorrow.
Check road conditions before traveling! pic.twitter.com/cw7SVeUm0F
A low-pressure system would move east of the North Island from later today, spreading strong and cold south to southwest winds over areas south of Auckland, including the capital.
"During Monday morning and afternoon gale southerlies are expected to develop along the South Island east coast, with severe gales expected about Wellington and the Marlborough Coast and Sounds from Monday evening and a warning is now in force."
Many North Island places would struggle to reach the low teen's during the day, with 10C the maximum in Wellington from Tuesday to Thursday and 13C for Napier, Best said.
"People should layer up clothing-wise and be prepared for deteriorating weather conditions."
Slips are already coming down as Wellington braces for galeforce winds and heavy downpours.
The MetService has issued a strong wind warning and a heavy rain warning for the region.
From midday a period of persistent rain with heavy falls is forecast.
Later in the afternoon southerlies are expected to rise to gale force gusting as strong as 120kmh in exposed places through into the night.
Metservice meteorologist Lisa Murray said the wind and rain would continue until tomorrow morning.
"So quite a blast of southerlies some really cool temperatures over the next few days. Maximum temperatures are really just getting past 10 maybe 11 degrees."
A slip has already fallen onto the front of a car on Ohiro Road in Brooklyn.
Wellington City Council said contractors were on route to the incident and traffic management has been auctioned.
Another slip came down on the westbound lane of State Highway 58 earlier this morning, but has since been partially cleared.
A council spokeswoman said people should make sure their gutters are clear and trampolines are tied down.
From Northland to Taranaki and across to Taupō and Bay of Plenty, there was a moderate risk of thunderstorms developing from about dawn.
"A lower risk of thunderstorms extends to most remaining areas of the North Island north of Wellington and to western Nelson and Buller in the northwest of the South Island," Best said.
The forecast was not unexpected as the transition from winter to spring often brought turbulent weather, Best said.
"Seas are still relatively cold around Aotearoa, but as the subtropics start heating up quickly and temperatures remain cold to the south us, the thermal contrast can result in strong spring winds.
"We can also still experience very cold outbreaks, as southerly changes push up the country from the Southern Ocean."
Road snowfall warnings are in place for Desert Road (SH1), Lewis Pass (SH7), Arthur's Pass (SH73), Porters Pass (SH73), Haast Pass (SH6), Lindis Pass (SH8), Crown Range Road and the Dunedin to Waitati Highway (SH1).
As a southerly change bullies its way northward tomorrow, some rough seas are expected in the Cook Strait.
— NIWA Weather (@NiwaWeather) September 2, 2018
Check out our regional modelling, which highlights wave heights up to 6m during Monday evening 🌊🌊🌊 @interislander pic.twitter.com/qExX45GN7Q
Whangarei: Showers, some heavy with hail and chance thundery. Northwesterlies. High 14C Low 6C
Auckland: Showers, some heavy with hail and chance thundery, clearing at night and northwesterly change southerly. High 14C Low 6C
Tauranga: Showers, some heavy with hail and chance thundery, clearing late evening and northwesterly dying out. High 14C Low 5C
Rotorua: Showers, some heavy with hail and chance thundery, clearing late evening and northwesterly dying out. High 12C Low 3C
New Plymouth: Showers, some heavy with hail and chance thundery, clearing evening as northwesterlies change strong southeast. High 13C Low 6C
Napier: Fine with northwesterlies until late afternoon, then a southwesterly change brings cloudy periods and a few showers. High 18C Low 5C
Whanganui: Morning cloudy periods, then a cold afternoon southerly brings rain, heavy at times with hail. Winds strengthening evening. High 15C Low 7C
Wellington: Showers then rain with possible heavy falls from around midday with southerly gales gusting 120 km/h. High 13C Low 6C
Christchurch: Rain, with snow above 400 metres, easing to showers afternoon. Strong cold southerlies, gale in exposed parts, easing. High 9C Low 6C
Dunedin: A few showers. Strong cold southerlies, gale at first, easing this afternoon. High 10C Low 7C