An "Antarctic snap" is expected to set the country shivering later this week, but not before heavy rain sends much of the North Island reaching for the raincoats and umbrellas.
It will be a wet start to the week after the Queen's Birthday holiday, MetService said, but as next weekend draws closer it will be time to pull out those winter woolies again.
The South Island was in for an "Antarctic snap", WeatherWatch said, with a "pretty sudden drop in temperature" as a cold southerly flow spreads over the region.
A number of heavy rain warnings are in place to start off the week for the northern half of the North Island and the upper South Island, with most of the North Island likely to see periods of rain tomorrow.
Bursts of heavy and possibly thundery rain are expected in northern and central New Zealand during Tuesday and Wednesday, with the heaviest falls likely in Nelson, the Richmond Range and Mt Taranaki, Tongariro National Park, Bay of Plenty and the far north of Gisborne.
Falls of 100mm to 140mm of rain could be expected in those areas over a 12- to 27-hour period, MetService warned.
Several watches are also in place for Northland, Auckland, Waikato and the Coromandel Peninsula, Waitomo, Taumarunui and Taranaki for heavy rain on Tuesday. A similar watch is in place for Marlborough and Buller.
There could also be severe gales in Auckland and Northland later on Wednesday and early Thursday.
"Over the next couple of days we have a complex low crossing over New Zealand. That low centre should pass over on Wednesday and behind the low centre we expect a southerly to push up the country," MetService meteorologist Hannah Moes said.
"So we're looking at colder temperatures with that southerly coming on, so for the South Island that will begin from Wednesday, and that will push into the North Island on Thursday."
But as the low crosses the country it will bring periods of rain, which will affect most areas, but particularly those in the north and west, she said.
As the southerly approaches, snow will fall to low levels in the south, Ms Moes said.
On Thursday there would be rain or showers for most places "again", she said, but in the South Island the skies will clear except in the far south where it's expected to snow.
Rain is forecast to snow above 500m on the Milford Road, Lindis Pass and Porters Pass tomorrow night but is forecast to clear by early on Thursday, MetService said.
WeatherWatch said a cold southerly airflow was set to spread over the lower half of the the country this week, describing it as an "Antarctic snap".
"Some places can look ahead to snow flurries, though most of the worst of the weather should pass by Friday this week, and most of the heavy stuff should stay where it belongs - on the ski fields," the forecaster said.
Invercargill could expect to see snowfall of 4cm down to 800m by Thursday, WeatherWatch said. They may be around 1cm of snow down to 300m in the afternoon, before clearing again.
Main centres forecast
Dunedin - Expect morning rain on Tuesday, before fine breaks in the afternoon, a northeast wind dies out, and a high of 13C. Rain develops on Wednesday, with a cold southwest change coming in, a high of 12C.
Auckland - Expect heavy rain on Tuesday, easing to showers in the afternoon, a fresh northerly and a high of 19C. Showers on Wednesday, some heavy and with a chance of thunder, northwesterlies and a high of 17C.
Hamilton - Rain on Tuesday, possibly heavy, turning to showers in the afternoon, a northeast wind and a high of 18C. Expect showers on Wednesday, some heavy and with a chance of thunder, northwesterlies and a high of 16C.
Tauranga - Tuesday should see rain, becoming heavy in the afternoon, strong northeasterlies and a high of 18C. Occasional showers on Wednesday, northwesterlies and a high of 17C.
Wellington - Cloudy on Tuesday, with occasional rain, northerlies and a high of 17C. Wednesday turns cloudy again with occasional rain, northerlies and a high of 15C.
Christchurch - A period of morning rain on Tuesday, then fine spells, a dying northeasterly and a high of 16C. Wednesday will see rain developing and a cold southwest change, a high of 13C.
(Source: MetService)
- Patrice Dougan of NZME. News Service
