A big low causing havoc in parts of Australia will mostly spare New Zealand - but we're still in for plenty of wet and rain over the next couple of days.

A smaller secondary low affecting the country today should be short lived, Weather Watch head analyst Philip Duncan said.

The main low won't reach us until Tuesday, where it was forecast to fall apart as it crossed the South Island on Wednesday.

Nevertheless, cloud and rain would be sticking around for the next few days and MetService had weather watches out for parts of the upper North Island.

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A severe rain watch is in place for Westland, south of Hokitika, to 11pm tonight, where up to 120mm is forecast in the ranges.

Northwest of Nelson and Mt Taranaki could also get some heavy falls through to this afternoon.

MetService meteorologist April Clark said the story "wouldn't be changing much" over the weekend.

Tomorrow was forecast to be "a dull day for a lot of people in the North Island and rainy in the upper north, but not so bad for the South Island".

On Saturday and Sunday, a low over the western Tasman Sea is expected to maintain a moist north to northeast flow over the country.

There will likely be heavy rain across the upper North Island Saturday, and in western areas on Sunday, especially in the Bay of Plenty and Gisborne ranges, where it may continue into Monday.

Temperatures are forecast to stay fairly mild in the North Island because of the northerly flow. Auckland is forecast to hover around 20C through to mid next week.

The South Island, however, is in for a cool southerly change on Saturday. Christchurch drops to a maximum of 14C and 11C on Sunday.

Temperatures are forecast to remain in the low teens across the South Island through next week.

On Monday, the rain looks like clearing over the North Island but there could still be a showery northwest flow.

Today's weather

• Whangarei
Cloudy. Showers developing morning then rain by evening. Northerlies. 22C high, 17C overnight.

• Auckland
Cloudy. Showers developing morning, turning to rain afternoon. Northerlies. 20C high, 16C overnight.

• Hamilton
Cloudy, showers developing in the morning, then rain from afternoon. Northerlies. 19C high, 15C overnight.

• Tauranga
Morning showers then rain from afternoon. Northerlies. 20C high, 16C overnight.

• New Plymouth
Periods of rain, easing to showers evening. Strong northerlies, easing evening. 19C high, 12C overnight.

• Napier
Cloudy, with occasional light rain until evening. Northerlies. 19C high, 13C overnight.

• Wellington​
Occasional rain. Northerlies, becoming strong in the afternoon. 17C high, 12C overnight.

• Nelson​
Rain developing morning with brisk northerlies, clearing evening. 18C high, 11C overnight.

• Christchurch​
Overcast until afternoon with rain at times, then becoming fine and northeasterlies easing. 16C high, 9C overnight.

• Dunedin​
Overcast, and rain at times from late morning. Northeasterlies changing to brisk southwesterlies evening. 14C high, 8C overnight.