Weather: Flooding possible as parts of New Zealand brace for a month of rain in one week

A month of rain will fall in just a week for parts of New Zealand, thanks to a large low making its way across the Tasman in the coming days.

The low is expected to bring massive downpours for some regions - including more than 120mm in inland parts of the North Island, Nelson, Taranaki, south Waikato and inland Bay of Plenty - which could bring flooding.

NIWA Weather says warm seas north of Australia are supplying the moisture to the low, which is anticipated to make landfall in New Zealand on Tuesday before petering out on Thursday.

Latitudinally central parts of the country will be our wettest, with our northernmost and southernmost regions likely to get less than 30mm of rain in the next week.

"Not everyone will get big rainfall totals. Northland, Gisborne, Southland and Otago all have low numbers, as does the very eastern and southern parts of Canterbury," said Weather Watch.

"Auckland, with water restrictions in force since May, is right on the boundary for heavier falls."

MetService has put heavy rain watches in place for Taranaki and Bay of Plenty on Tuesday, and say these will likely be escalated to warnings later this week.

Weather Watch says flooding is possible in both islands due to the forecasted deluge - but it's not just rain they're worried about.

On Wednesday, Weather Watch predicts strong easterlies will batter the upper South Island, while nor'westers in Auckland are predicted to rise to gale force levels in exposed areas.

"Winds will be blustery later on Tuesday from the north and will having varying directions as the low itself moves in. Gales are possible in Auckland from the north and west, while easterlies are likely to reach gale around Cook Strait," Weather Watch continued.

"Generally speaking, due to the low weakening, winds shouldn't be too much of a headache - but some power cuts are possible due to the risk of tree branches breaking here and there."