"Tonight and tomorrow morning will be very cold across the country. From pretty much Hamilton south we can expect frosts and freezing temperatures."
On Friday a ridge of high pressure would cover most of New Zealand, bringing mostly settled weather.
On Saturday however, a front would arrive from the Tasman Sea, affecting the lower west coast of the South Island, with potential for heavy rain in Fiordland and southern Westland.
In the North Island from late Saturday a strong, moist northeast flow would spread on to the upper areas, bringing rain and northeast gales to many places.
On Sunday east and northeast winds could reach gale about Northland to East Cape and Waikato.
There could also be heavy rain about Northland, Coromandel Peninsula, and parts of Auckland.
On Monday this system would spread further over the North Island and central New Zealand, bringing potentially heavy rainfall over Gisborne, easternmost Bay of Plenty, and from Marlborough Sounds to northern Buller.
Today's weather
Whangārei
Mainly fine, could get a morning shower. Southwest dying out this morning. 16C high, 7C overnight.
Auckland
Fine apart from isolated morning showers. Southwest dying out afternoon. 16C high, 5C overnight.
Hamilton
Cloudy at times, chance shower. Southwesterlies dying out this afternoon. 15C high, 2C overnight.
Tauranga
Cloudy at times. Chance shower from afternoon. Southwesterlies dying out afternoon. 16C high, 6C overnight.
New Plymouth Showers clearing this afternoon. Westerlies dying out around midday. 14C high, 4C overnight.
Napier Fine apart from few showers late morning. Southwest change. 13C high, 2C overnight.
Wellington A few showers around dawn with a fresh southerly change, then fine and winds dying out. 11C high, 4C overnight.
Nelson Fine, but chance morning shower. Light winds. 11C high, 4C overnight.
Christchurch Morning cloud and chance shower then fine. Southwesterlies dying out. 10C high, -2C overnight.
Dunedin Fine. Southwesterlies dying out this afternoon. 10C high, 2C overnight.