A low pressure system over the upper North Island is drifting westwards during today and slowly weakening, says MetService.

This weather system is bringing a moist east to northeast flow to northern and central New Zealand.

Northland and Auckland have areas of morning fog. Showers may become widespread, with thunderstorms possible north of Whangaparaoa.

For Bay of Plenty, Taupo, Gisborne, Hawke's Bay and Wairarapa, expect periods of rain, with some heavy and possibly thundery falls, easing in Bay of Plenty this afternoon.

Coromandel Peninsula to Whanganui, including Taumarunui and Taihape, will have a partly cloudy day with isolated showers clearing this evening.

Heavy Rain Watches remain in force for northern Hawke's Bay, Wairarapa and Tararua District and eastern Marlborough.

Heavy Rain Warnings are in place for Hawke's Bay south of Te Pohue and Gisborne/Tairawhiti.

There is still uncertainty with the distribution and intensity of the heaviest rain, and people are advised to keep up to date with the latest forecasts in case any changes are made or new areas are added.

A Heavy Rain Watch is in place for the following areas:
Area: Hawke's Bay north of Te Pohue
Valid: 23 hours from 10:00pm Sun 18 Jun to 9:00pm Mon 19 Jun
Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria, especially about the ranges. Thunderstorms are possible.
Note, another burst of heavy rain is possible during overnight Monday and this watch may be extended.

Area: Wairarapa including the Tararua District
Valid: 29 hours from 10:00pm Sun 18 Jun to 3:00am Tue 20 Jun
Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria, mainly about the ranges.

A Heavy Rain Warning is in place for the following areas:
Area: Gisborne/Tairawhiti
Valid: 20 hours from 10:00pm Sun 18 Jun to 6:00pm Mon 19 Jun
Forecast: Expect 70 to 100 mm of rain. Peak rates of 15 to 25 mm/h, especially in thunderstorms.
Note, another burst of heavy rain is possible during Monday evening and this warning may be extended.

Area: Hawke's Bay about and south of Te Pohue
Valid: 26 hours from 10:00pm Sun 18 Jun to 12:00am Tue 20 Jun
Forecast: Expect 100 to 140 mm of rain, mainly about the ranges. Peak rates of 15 to 25 mm/h in thunderstorms.
Note, the heaviest rain is expected about the inland ranges and the coastal hills and ranges south of Napier.

Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.