Metservice is forecasting a weakening high covering the North Island on Tuesday, while a weakening front will be moving north over the South Island.

During Wednesday, a sub-tropical low is expected to be moving southwards towards the north of the country, bringing rain in a strengthening east to southeast flow to the northeast of the North Island.

"The sub-tropical low should move to the east of the North Island late Thursday,' says a MetService spokesperson.

"There still remains uncertainty with precisely how the sub-tropical low will track and impact New Zealand, but there is an increase in confidence it will bring a period of rain with possible heavy falls to Gisborne.

"Consequently, from the second half of Wednesday until late Thursday, there is moderate confidence for warning amounts of rain in Gisborne, while for Hawke's Bay north of Napier, there is low confidence for warning amounts of rain during Thursday," says a MetService spokesperson.

"Additionally, for the eastern Bay of Plenty east of Whakatane from Wednesday and into Thursday, there is low confidence east to southeast winds could rise to severe gale in exposed places."

For the South Island, a front from over the south Tasman Sea is expected to reach Fiordland Thursday evening, then weaken as it moves over the South Island during Friday.

"There is low confidence that the front will bring warning amounts of rain to Fiordland from Thursday evening to Friday morning."