Rain, thunderstorms, snow, strong winds and big swell are all threatening to batter New Zealand as a strong Southern Ocean front moves up the country.
MetService is issuing warnings and watches for heavy rain, heavy snow and severe gales for many parts of southern and central New Zealand as a "serious low" bulldozes over the nation tonight.
"A deepening low and an active front are expected to move northeast across the South Island today, then over the North Island on Tuesday," MetService warns.
"Strong and moist northwest winds precede the front, and is followed by a strong cold southerly change."
NIWA has compiled a list of possible weather hazards on what it calls a "meteorologically manic Monday".
WINDS TO 'LASH' NZ
Widespread strong winds are expected over the coming days as northwesterlies pick up ahead of the fronts today and blustery southwesters impact tomorrow.
"Strong nor'west winds will lash the western and northern South Island before moving into Wellington Monday evening," NIWA warns.
"A blustery southerly will develop in the coastal South Island on Monday night, including for Dunedin and Christchurch."
MetService says all three main cities can expect strong winds overnight - a sign of their scale.
"Strong and gusty winds are expected for Auckland, Wellington and Christchurch. This just illustrates the broad nature of these strong winds," MetService meteorologist Mmathapelo Makgabutlane says.
HEAVY RAIN WARNINGS ISSUED
As the fronts make their way up the South Island today, they'll deliver heavy rainfall for the western parts where heavy rain watches and warnings are in place.
"The bulk of that rain will be for the western South Island today, extending to elevated parts of the North Island tomorrow," Makgabutlane explains.
A heavy rain warning is in place for the ranges of Westland south of Otira between 10am - 9pm Monday with 70 to 100mm of rain expected to accumulate.
Another heavy rain warning was in place for Fiordland until 2pm today, with another 50 to 70mm of rain to accumulate on top of what has already fallen.
'MARKED FALL' IN TEMPERATURE
A rush of cold air behind the fronts turns showers into snow for the lower and central South Island.
MetService says snowfall could be heavy for parts of Otago and Canterbury from Monday into Tuesday morning, and areas down to 400 metres will likely get some October snowfalls.
"Motorists are advised to plan their journeys ahead as snowfalls may affect high level roads and passes," Makgabutlane says.
That cold air means there will be a "marked fall" in daytime temperatures midweek, with most of the South Island reaching maximums in the low-teens and single digits. Christchurch only rises to 9C on Wednesday, a major drop from the 23C enjoyed last week.
SWELLS AND ROUGH SEAS
After the low crosses New Zealand it will deepen into an offshore storm across Tuesday and Wednesday.
"The bulk of the worst gales will be mainly at sea, but they will likely brush eastern coastal areas late Tuesday/early Wednesday," WeatherWatch states.
This will churn up some heavy seas and big waves - and the public is urged to stay safe.
"Rough seas will affect coastal areas of the eastern South Island & lower North Island + Chatham Island," NIWA warns.
