MetService has issued a Heavy Rain Warning with heavy rain and northerly gales expected across western and northern parts of New Zealand today.

A front that was moving across the upper South Island on Saturday night is forecast to continue moving across the North Island during Sunday.

The front is expected to bring a period of heavy rain and northerly gales to parts of the country, with Warnings and Watches for Heavy Rain and Strong Winds in force.

A low is expected to deepen east of the North Island on Monday bringing a period of strong south or southwest winds to northern and central New Zealand during Monday and Tuesday.

There is moderate confidence that southerly winds will reach severe gale for a time about northern Hawke's Bay and Tairawhiti/Gisborne late Monday and Tuesday, and low confidence of severe gales over many other parts of the North Island, as well as coastal Marlborough and Kaikoura, during the same time.

There is also low confidence that southerly rainfall amounts could reaching warning criteria about the hills and ranges of northern Hawke's Bay and southern Tairawhiti/Gisborne on Monday and Tuesday.

The southerly flow eases on Wednesday. A trough and associated rain-band is likely to move onto the South Island on Thursday, but the risk of severe weather with this feature is considered minimal.

People are advised to keep up to date with the latest forecasts in case any changes are made.

Heavy Rain Warning is in place for the following regions:

Area: Bay of Plenty east of Kawerau and Tairawhiti/Gisborne north of Ruatoria
Valid: 21 hours from 12:00am Sun 20 Aug to 9:00pm Sun 20 Aug
Forecast: Expect 100 to 140 mm of rain, where highest accumulations are expected about the ranges. Peak rates of 15 to 20 mm/h expected during Sunday morning and afternoon.

Area: Mount Taranaki
Valid: 13 hours from 8:00pm Sat 19 Aug to 9:00am Sun 20 Aug
Forecast: Periods of heavy northerly rain. Expect a further 60 to 80 mm of rain on top of what has already fallen. Peak intensities of 15 to 20 mm/h.

Area: Tasman, about and west of Motueka
Valid: 4 hours from 8:00pm Sat 19 Aug to 12:00am Sun 20 Aug
Forecast: A period of heavy northerly rain. Expect a further 30 to 40 mm of rain on top of what has already fallen. Peak intensities of 15 to 20 mm/h.

Area: The ranges of Westland south of Otira
Valid: 4 hours from 8:00pm Sat 19 Aug to 12:00am Sun 20 Aug
Forecast: A period of heavy northerly rain. Expect a further 30 to 40 mm of rain on top of what has already fallen. Peak intensities of 10 to 15 mm/h.

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

Warnings no longer in Force
Strong Wind Warning lifted for Fiordland about the fiords: Northeast gales have eased.

A Heavy Rain Watch is in place for the following regions:
Area: Northland and Auckland including Great Barrier Island
Valid: 15 hours from 8:00pm Sat 19 Aug to 11:00am Sun 20 Aug
Forecast: Periods of heavy rain, and amounts may approach warning criteria in localised areas.

Area: Waikato, Coromandel Peninsula, Taupo, and Bay of Plenty about and west of Kawerau including Rotorua
Valid: 11 hours from 2:00am Sun 20 Aug to 1:00pm Sun 20 Aug
Forecast: Periods of heavy rain, and amounts may approach warning criteria in localised areas.

Area: Central North Island hill country from eastern Taranaki to Taihape, and northwards to Waitomo
Valid: 16 hours from 8:00pm Sat 19 Aug to 12:00pm Sun 20 Aug
Forecast: Periods of heavy northerly rain, and accumulations may approach warning criteria.

Area: Bryant and Richmond ranges including the Rai Valley
Valid: 6 hours from 8:00pm Sat 19 Aug to 2:00am Sun 20 Aug
Forecast: Periods of heavy rain, and accumulations may approach warning criteria.

Area: Buller
Valid: 4 hours from 8:00pm Sat 19 Aug to 12:00am Sun 20 Aug
Forecast: A period of heavy northerly rain with possible thunderstorms, and accumulations may approach warning criteria

Area: Fiordland north of Doubtful Sounds
Valid: 13 hours from 8:00pm Sat 19 Aug to 9:00am Sun 20 Aug
Forecast: Periods of heavy rain, and amounts may approach warning criteria.

Strong Wind Watch
Area: South Taranaki, Taihape, and Whanganui north of the City
Valid: 3 hours from 8:00pm Sat 19 Aug to 11:00pm Sat 19 Aug
Forecast: Northerly winds may approach severe gale in exposed places.

Area: Canterbury High Country
Valid: 8 hours from 8:00pm Sat 19 Aug to 4:00am Sun 20 Aug
Forecast: Northwest winds may approach severe gale in exposed places.

Watches no longer in Force
Strong Wind Watch lifted for Tasman and Nelson: Northerly gales have eased.