An "atmospheric river" is heading towards New Zealand next week, and is forecast to bring heavy rain and possible flooding on Monday and Tuesday.
A NIWA graphic shows the plume of moisture-laden air coming down out of the Pacific and striking the country.
"At this time, the regions most likely to experience heavy falls include the northern and western North Island and northern and eastern South Island," NIWA said on Facebook.
"The purple colours in the animation indicate very high moisture values - ones we'd associate with a flooding risk."
MetService said a front is expected to bring some heavy rain and strong northerly winds to parts of northern and central New Zealand early next week.
There's a high confidence that rainfall amounts will reach warning criteria in the far north of Gisborne and Bay of Plenty, and a moderate confidence for Northland, Auckland and Coromandel Peninsula, especially in eastern areas.
There's also a low confidence for the remainder of the upper North Island from Taranaki across to the Gisborne ranges northwards, as well as for the Tararua District and Ranges, Wairarapa, Wellington, the Marlborough Sounds and coast, and northwest Tasman.
Then on Tuesday, there is moderate confidence of heavy rain below about 500 metres for Canterbury, with moderate confidence of heavy snow above about 500 metres for the region.
