9.10am update: MetService has issued a Severe Weather Warning for parts of the South Island.

A moist northerly airstream is expected to bring further heavy rain to Nelson and Marlborough today and into Sunday.

Heavy rain is possible for western parts of the South Island later on Sunday, Monday and Tuesday.

People are advised to keep up to date with the latest forecasts since the amount of rain expected could cause slips, localised flooding and damage to roads.

Heavy rain Warning

A Heavy Rain Warning has been issued for the following regions:

Area: Marlborough about and north of the Awatere Valley, also Nelson and Tasman south and east of Motueka
Valid: 12 hours from 9:00am Sat 6 May to 9:00pm Sat 6 May
Forecast: Expect a further 70 to 100 mm of rain with the largest accumulations about the ranges, in addition to what has already fallen. Peak rates of 15 to 25 mm/h this morning and early afternoon.

Area: Tasman from Motueka westwards
Valid: 30 hours from 9:00am Sat 6 May to 3:00pm Sun 7 May
Forecast: Expect a further 110 to 160 mm about the ranges and 70 to 100 mm near the coast. This is in addition to what has already fallen. Peak rates of 15 to 25 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.

Heavy Rain Watch

A Heavy Rain Watch has been issued for the north and west of the South Island, affecting these regions:

Area: Buller

Valid: 20 hours from 10:00pm Sat 6 May to 6:00pm Sun 7 May
Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria.

Area: Westland
Valid: 48 hours from 11:00pm Sun 7 May to 11:00pm Tue 9 May
Forecast: Periods of heavy rain. Rainfall amounts may exceed warning criteria and it is likely that this watch will be upgraded to a warning closer to the event.

A stationary front is feeding into the upper South Island today bringing heavy rain, says a Weatherwatch spokesperson.

Heavy rain is also expected for some western North Island areas but will be easing around midday.

For Bay of Plenty, Northland, Auckland, and Waikato the weather is expected to be humid with occasional showers. Morning rain for Northland will be easing, and northeasterly winds are forecast. Highs for these regions should be between 19-22 degrees Celsius.

Western North Island (including Central North Island)
Mostly cloudy with spits or showers, heavy rain for Taranaki and Kapiti eases by midday. Some sun may break through from afternoon. Northeasterly winds.
Highs: 16-23

Eastern North Island
Sun and high cloud, a few spits or showers for Wairarapa clearing during the afternoon. Northeasterly winds.
Highs: 22-23

Wellington
Rain, easing around midday to spits and showers. Gusty northerlies ease later in the day.
Highs: 19-21

Marlborough & Nelson
Rain, heavy for Tasman, Nelson and the Sounds. Perhaps easing in the afternoon then picking up again overnight. Northerly winds.
Highs: 19-20

Canterbury
Mostly sunny, some high cloud. North to northwesterly winds.
Highs: 18-21

West Coast
Cloudy areas and showers, thinning out in the afternoon with sun breaking through. Later in the day or overnight rain pushes down from the north. Northeasterly winds.
Highs: 16-19

Southland & Otago
Mostly sunny, any morning cloud breaks away. Light winds.
Highs: 19-21