Canterbury is bracing for a deluge of heavy rain this weekend, as authorities issue a rare warning only given for extreme weather events.
The MetService has put out a red warning notice for heavy rain for Canterbury and multiple warnings in others parts of the South Island, in particular.
"This is only the second red warning issued by MetService and will be a significant weather event," a statement said.
Meteorologist Alwyn Bakker said between 200mm to 300mm of rain is forecast to accumulate about the Canterbury high country and foothills during that time - with 80mm to 120mm of rain further east about the plains and coast.
"This is from 3 o'clock today through to Monday - so it's going to be a significant period of a lot of rainfall," he said.
"A red warning is when it's going to be a significant weather event. In this particular case, it's going to be a lot of rainfall.
"We're expecting dangerous river conditions and significant flooding."
The wild weather comes as a complex low pressure system over the Tasman Sea is set to slowly move south-eastwards across northern and central New Zealand this weekend.
It is then forecast to move to the east on Monday.
"This system is expected to direct a strong and moist south-east flow across the South Island during this time - delivering an extended period of significant heavy rainfall to Canterbury and severe gale south-easterlies along the South Island west coast."
Rainfall set to be doubled
WeatherWatch said the system might bring more than double or even triple the amount of rain Christchurch gets in a month.
"Christchurch normally averages 64mm in May. But this weekend, WeatherWatch is forecasting 91mm for the city.
"This may change a little up or down. But generally speaking, it's a significant amount of rain forecast for the low-lying, quite-dry city."
MetService warned this was expected to be a "significant heavy rainfall event" for the whole of Canterbury.
A red warning notice is also in force in Amberley, and an orange warning for heavy rain is in force for the region from Amberley to Kaikōura.
Locals are told to keep a close eye on weather updates and warnings.
The rest of the country, including Auckland, is in for some kind of rain this weekend - whether it be scattered rain or showers.
Aucklanders are waking up to a crisp Saturday morning, with a temperature of almost 15C at 9am.
A high of 17C is forecast in the City of Sails and an overnight low of 9C will mean an extra blanket tonight.
The coldest place in the country, at 9am, was in Twizel, which recorded 3.2C.
The warmest place was Whakatāne, where 15.7C was recorded.
The windiest spot was at New Plymouth Airport, which clocked up to 41km/h winds.
The wettest place was Blenheim, where 4.2mm of rain had accumulated.
Periods of rain or showers - some heavy with possible squally thunderstorms - are on the cards for Northland to Taranaki, including Bay of Plenty and Taupō.
Heavy rain warnings
People in the Canterbury region are reminded that the heavy rain warning in Canterbury south of Amberley is in place from 3pm today until 11am on Monday.
MetService said people could expect peak hourly rates of between 10mm to 20mm/h - especially from later today and during tomorrow.
"Also note, the freezing level is forecast to be around 1400m [today], then lifting to around 1800m [tomorrow]." It will then lower to 1400m on Monday.
"Heavy snow is expected above the freezing level throughout the event. But heavy snow may fall as low as 1000m in some places at times - especially [tomorrow] and on Monday."
Weather experts said dangerous river conditions and flooding were expected.
Slips and floodwaters could disrupt travel, and conditions might make some roads impossible to travel on.
People are also being warned the conditions could result in some communities being isolated for some time.
There is also a heavy rain warning in Nelson west of Motueka (between 7am to 8pm today), where anything between 100mm to 130mm of rain is set to accumulate - especially around the ranges.
Thunderstorms are possible there, too.
Strong wind warnings
Strong wind warnings have been issued in Westland south of Hokitika and Fiordland.
Strong wind gusts have the potential to damage trees, powerlines and unsecured structures.
As a result, locals are encouraged to tie down or secure any outside furniture or bins.
"Driving may be hazardous, especially for high-sided vehicles and motorcycles."
Heavy rain and strong wind watches
Heavy rain watches are also in place in parts of the country - from the Bay of Plenty east of Whakatāne, Taranaki about and north of the mountain, the Richmond Range including the Rai Valley and down to Marlborough between Ward and Kaikōura.
A strong wind watch is in place in Buller and Westland about and north of Hokitika - from 1pm to 9pm today.
Road snowfall warnings
Anyone due to venture out is told to monitor MetService's road snowfall warnings and alerts.
Lewis Pass, Arthur's Pass, Porters Pass and Crown Range Rd all have current warnings.
For Lewis Pass (State Highway 7), the warning is valid from 11am to 2pm today. People travelling on this road are warned that snow may affect it until early this afternoon. Between 1cm to 3cm of snow could settle on the road near the summit.
Those braving the weather via Arthur's Pass (SH73) are told that snow is expected to affect the road from this evening through to tomorrow morning - from 8pm to 10am tomorrow.
Expect between 1cm to 3cm of snow to settle on the road near the summit - with lesser amounts down to 800m during this time, MetService says.
The warning on Porters Pass (SH73) is valid for 14 hours from 8pm to 10am tomorrow as well.
The Crown Range Rd has a three-hour warning from 11am to 2pm today.
Another update on the road snowfall warnings will be issued by 10pm by MetService.