The good news is a southerly front blasting the country south of Taranaki should be gone by the weekend.

The bad news is it won't start to back off until tomorrow.

The active southerly front arrived in Fiordland and Westland early this week, dumping more than 300mm of rain before slowly moving east across the South Island and north to Taranaki yesterday.

"A slow-moving front is now over central New Zealand, bringing periods of rain, heavy in some places," Metservice meteorologist Micky Malivuk said.

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"The front is forecast to gradually ease on Friday, and the weather to improve somewhat over the weekend as a ridge builds."

Temperatures have plummeted with the southerly system's arrival. Christchurch dropped 10C, from 24C yesterday to 14C today. Dunedin has a forecast high of 12C and Wellington 18C with heavy rain.

"Anywhere south of Taranaki will struggle to make it above the teens today," Malivuk said.

"That is the boundary between the cold and warm air."

Severe weather watches are in place for parts of the South Island and lower and central North Island.

Kapiti, Wellington and Marlborough north of Cape Campbell are under watch to 11am this morning, as up to 50mm is expected in six hours.

Watches in Dunedin and North Otago end at 8am and parts of Southland had heavy rain overnight.

Rain showers are forecast today for most of the South Island and the lower and central North Island, plus possible thunderstorms.

Eastern-facing parts of the North Island could experience some showers from an easterly flow. Areas from Auckland north should have a day of fine spells mixed with isolated showers.

New Plymouth had some of the heaviest falls yesterday. One rain gauge recorded 84mm over a two-hour period, Malivuk said.

Parts of the South Island recorded 50 to 60mm and snow was forecast down to 800m in places.

The front is forecast to weaken tomorrow and a ridge build on Saturday and Sunday, bringing more settled weather.

"We can expect a few showers about on Saturday, mainly from that easterly flow, but it is expected to ease through the day and clear up for Sunday."

Today's weather

Whangarei

Cloudy periods with the odd shower. Easterly breezes. 23C high, 16C overnight.

Auckland Mainly fine, but isolated afternoon showers, possibly heavy. Light winds. 24C high, 16C overnight.

Hamilton Fine spells. However, a few showers from afternoon, some heavy with possible thunderstorms. Light winds. 23C high, 13C overnight.

Tauranga Fine spells, and a few showers. Easterly breezes. 22C high, 16C overnight.

New Plymouth Occasional rain developing morning, chance heavy. Northerlies. 21C high, 14C overnight.

Napier Cloudy periods, chance shower from afternoon. Northeast developing in the morning. 23C high, 13C overnight.

Wellington
Rain, with possible heavy falls this morning. Strong cool southerlies. 18C high, 11C overnight.

Nelson​ Rain at times. Northeasterly developing this morning. 19C high, 11C overnight.

Christchurch​ Rain, easing from afternoon and clearing in the evening. Cold, strong southwesterlies, easing afternoon. 14C high, 8C overnight.

Dunedin​ Rain, easing from afternoon, clearing evening. Cold southerlies, strong this morning. 12C high, 9C overnight.