Take a breath when the rain stops, because there's now a bigger system on its way, with already sopping northern areas the first to face it.

MetService has issued a severe weather watch for seven parts of the country that it anticipates will be hit the hardest by what is expected to be widespread rain late on Thursday and into a particularly wet Friday.

It will be the second downpour of the week for a number of places, with Northland and Bay of Plenty already hit squelching from the first on Tuesday night.

MetService meteorologist Dan Corrigan says a 'decent dose” of between 55 and 70 millimetres of rain had fallen in the ranges east of Ōpōtiki and into Hicks Bay since Tuesday afternoon, while Northland had experienced up to 46mm of rain in the 24 hours to 6am on Wednesday – recorded in Parapara northeast of Kaitaia.

The majority of Northland and Auckland had experienced between 30mm and 45mm of rain in 24 hours.

MetService forecasters issued a new severe weather watch on Wednesday, saying Northland and Coromandel will bear the initial brunt of it.

Those two areas could experience heavy rain over a 24-hour period from 3pm on Thursday, which could possibly reach warning criteria.

Corrigan says Tuesday's rainmaker will continue to hang around and bring squally rain in Far North districts before 'wrapping around” the new system building in the northern Tasman Sea.

That system would move down across Northland, western areas of the North Island from Auckland to Taranaki, and Buller on the West Coast on Thursday, before sweeping across all of Aotearoa on Friday.

'Friday is looking like it's a wet day for everyone – it's going to be wet everywhere.”

Friday rain could exceed warning criteria in five regions – prompting five further heavy rain watches:

Severe weather could hit Bay of Plenty including Rotorua and into the ranges of Gisborne north of Ruatoria, the area around Taranaki Maunga, Tasman west of Motueka, Buller and Westland, MetService said.

Corrigan says once the low has established itself it will whip up winds potentially strong winds, and it will drop temperatures.

This means there's also the potential for heavy snow in the South Island High Country into the weekend, particularly to higher roads and passes.

Severe northwesterly gales are possible for exposed parts of Wellington, Horowhenua, Kāpiti Coast, Wairarapa and Hawke's Bay south of Hastings during Friday and Saturday and even exposed parts of Taranaki, Taihape and Bay of Plenty northwards.

Most of the rain in the south is likely to be more persistent on the West Coast though many eastern areas of the South and North Islands will also experience a dollop of rain on Friday.

-Stuff.