A new flooding threat is looming for the besieged Bay of Plenty where up to a month's worth of rain is forecast to fall in just under a day.

Much of central and northern New Zealand is under heavy rain warnings and watches as the remnants of ex-tropical Cyclone Donna injects moist tropical air into a sputtering low tracking slowly across the country.

Torrential rain is expected to fall tonight across an already-drenched North Island, bringing fresh fears of flooding and slips. Strong winds are also expected to buffet the top of the country.


The worst rain will fall over Nelson, Mt Taranaki, Bay of Plenty and the Gisborne ranges.

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The MetService is forecasting an intense 21-hour period of heavy rain over Bay of Plenty and the Gisborne Ranges. Up to 200mm is forecast to fall between 8pm today and 5pm Friday.


The rain was expected to take hold over the North Island this morning with heavy downpours in the top half.


Bay of Plenty Civil Defence has put the region on notice as it recovers from the damage left by back-to-back cyclones last month.

The heaviest rain was expected across Auckland tonight, including 100km/h gales in exposed areas.


However, the MetService said it was uncertain where the low would track and, if it changed course, this was expected to significantly affect the weather for each region.


In the latest swathe of weather warnings issued by MetService this morning forecasters warned the high rainfall would lead to rivers and streams swelling rapidly, flooding and slips.

As the remnants of Donna drifted south it was expected heavy rain and strong winds would lash northern regions as it tracked off the eastern coastline Friday and early Saturday.

Meteorolgists were monitoring this situation closely in case more warnings or watches were issued.

Weatherwatch.co.nz said downpours were likely to become torrential overnight and Friday.

It was possible the cyclone's rainy remnants could lead to flooding and slips across the North Island, especially on top of two ex-cyclones in recent weeks and other sub-tropical rain storms.

People were advised to keep up-to-date with warnings as the system developed.

Meanwhile, the Fiji Meteorological Service is bracing for the newly formed Tropical Cyclone Ella.

It is now a Category 2 storm lying to the northeast of Fiji.

It was expected to intensify as it moved closer to land.