New Zealand is under siege by a winter blast, with bitterly cold weather swathing several regions and thunderstorms set to unleash on parts of the country.
Rain is developing throughout central New Zealand, while snow is falling to low levels in Canterbury.
"We have active road snowfall warnings for all major alpine passes," MetService warns.
"In addition to the snow and wind, we are expecting some significant swell heights across Aotearoa, New Zealand in the coming days."
WeatherWatch says the swells could be damaging.
"Tonight Wellington and Wairarapa's coastline will be exposed to damaging southerlies which will help push up wave heights, into the zone where it may be problematic in places at high tide," the forecaster said on Sunday.
"Some waves may come over roads, especially in Wellington, bringing with it sand, driftwood and rocks.
"Wave heights are estimated to be between 4 and 6 metres with gale force southerlies gusting 120km/h at sea level and potentially over 140km/h higher up."
Wind warnings
A blast of cold air will affect parts of New Zealand on Sunday night and into Monday, but WeatherWatch says many New Zealanders are already feeling a temperature drop.
Strong wind warnings are in place for southern and eastern Wairarapa and Wellington and coastal Marlborough.
WeatherWatch warns the gusty winds will be widespread.
"Scattered thunderstorms and/or heavy downpours are possible in some areas of the North Island such as Auckland/Northland down to Taranaki.
"Gusty winds near 100 km/h are likely in coastal areas of the North Island around Cook Strait in early Monday, with gusts 120 to 140km/h in the more extreme exposed areas of the lower North Island and Marlborough Sounds."
Snow
Heavy snow warnings are in place for Marlborough south of Seddon, parts of Canterbury, the Tararua and Rimutaka Range, and Taihape. Snow is already falling to low levels in some areas in south Canterbury.
"Snow is possible down to sea level and is expected to become heavy inland above about 200 metres where 15 to 30 cm of snow is forecast to accumulate, or possibly more at higher levels," MetService said.
"Note, snow showers are likely to be at sea level tonight [Sunday] and Monday morning, these may affect Christchurch and Banks Peninsula."
There's also a risk of thunderstorms in some areas, with "an active line" about to pass through the Taranaki region.
"There is a moderate risk of thunderstorms with the front in some exposed areas as it sweeps northeast across the country," MetService said.
"This applies to the far west of Nelson this morning, the Marlborough Sounds, Wellington, Kapiti, Taranaki and the west of Waitomo and Waikato this morning and afternoon, and Great Barrier Island, much of the Bay of Plenty and the far north of Gisborne this afternoon and evening."