Most of the North Island lies under a severe thunderstorm watch ahead of a day of heavy rain and violent electrical storms.

All but Tairāwhiti is under a rain alert with rain and storms already beginning this morning.

A dozen warnings and watches are in place from Northland to Wellington.

The rain is expected to hit the City of Sails from 1pm today and last for 12 hours, while it is already falling in Taranaki and the central plateau.

The Bay of Plenty, where a heavy rain warning has been issued, is in for 25 hours of wet weather, including thunderstorms and a threat of flooding.

The severe thunderstorm watch comes into force in Northland at 11am and will last until midnight. Other thunderstorm alerts come into force from 1pm and last until Friday morning.

MetService meteorologist Lewis Ferris said while Auckland would escape wet weather this morning, there was a risk of showers that look “more persistent and widespread throughout the afternoon”.

“There is a risk of thunderstorms increasing throughout the second half of the day.

“We’re potentially seeing some quite heavy falls for the commute home from work, making things a bit slower.”

He estimated 10-20mm of rain an hour would be likely for most of Auckland.

“Through the afternoon, some isolated spots could see 25-40mm an hour.

“There is also a risk of thunderstorms for quite a large portion of the North Island in the second half of the day,” Ferris said.

A severe thunderstorm watch is in place for Taranaki until 11pm.

Ferris said that could be extended through the northern parts of the North Island.

A heavy rain warning is in place for the Marlborough Sounds, Richmond Range and the Rai Valley until 1pm where residents can expect 90-110mm of rain.

A heavy rain watch is in place for Marlborough south of the Richmond Range and for the Kaikōura coast until 3pm.

Heavy rain watches are also in place for Nelson and Tasman Districts north of Nelson Lakes, Buller north of Granity and for Wellington until early this morning.

Ferris said the Marlborough Sounds looked like the region where the most persistent and heavy rain would occur during the second half of today.

“Those surrounding areas, the rest of Marlborough, Nelson, Tasman and parts of Wellington will see a decent stretch of rain as we move through the day,” he said.

Temperatures across the North Island are forecast to remain in the mid-20s today.

However, the eastern and southern parts of the South Island are forecast to experience chillier conditions, with Christchurch reaching a high of 17C, and Dunedin, Oamaru and Invercargill reaching a high of 15C, according to Niwa Weather.