Parts of New Zealand can expect more than 30 hours of rain, with weather warnings and watches in place for both islands.

MetService says heavy rain warnings will continue for Eastern Bay of Plenty, Taranaki and the west coast of the South Island, while heavy rain watches are also in place for Northland, Tongariro National Park, Tasman and Buller.

Taranaki's heavy rain warning is in place for 48 hours with 300 to 400mm of rain expected near the mountain and 150 to 200 mm elsewhere.

Westland south of Otira, also had a warning in place for more than 30 hours, while watches for Northland and Tongariro National Park also spanned more than a day.

Things may ease off in the Bay of Plenty by the end of Wednesday as the active fronts are expected to meet in the middle, bringing heavy rain to Wellington and in Nelson.

MetService says heavy rain might cause streams and rivers to rise rapidly, with surface flooding and slips also possible.

Auckland awoke to fog on Wednesday at 6.30am, as the muggy week continued.

An Auckland Airport spokesperson say no flights in the region have been impacted by it.

'New Zealand is stuck in very warm moist air coming from the north,” says MetService forecaster Gerard Bellam

'We saw temperatures touching the mid-20s on Tuesday and warm temperatures [continuing] even overnights.

'It is being driven by the tropics and may stick around for quite a few days.”

Average temperatures were likely to be in the high teens and mid-teens for the North Island.

Further south, Dunedin could witness temperatures as high as 16 degree Celsius on Wednesday morning.

'Since warm air holds more moisture than cold air, significant rainfall accumulations are likely right through this weekend.”

- Shilpy Arora and Melanie Earley/Stuff.