Weather: Risk of hail, flash floods, tornadoes as thunderstorms set to batter New Zealand over next few days

After a wild end to last week for New Zealand, unsettled continues into this one as forecasters warn of potential hail, thunderstorms and tornadoes over the next few days.

Weather Watch says more heavy downpours are also in store for the North Island, bringing as much as 70mm of rain to the likes of Hakwe's Bay and Wairarapa on the island's lower eastern side.

Low pressure over the island will see cool and warm air mix, which could create thunderstorms throughout the afternoon and beyond.

Northland, Auckland, Waikato and the Coromandel are all at risk of seeing some on Monday, with the blustery conditions shifting to central and lower parts of the North Island on Tuesday.

"These thunderstorms will boost local rainfall rates, and there is a low risk that some of the thunderstorms could be severe with localised downpours of 25-40mm/h," MetService says.

"If severe thunderstorms do occur, they could cause surface and/or flash flooding and make driving conditions extremely hazardous."

Weather Watch says the North Island has the right conditions for thunderstorms, as a low-pressure system has stalled over the island, "essentially mixing warm and cool air with daytime heating".

"While some large sunny and dry areas are about, the atmosphere is more unstable. Light winds in northern areas today (and more central areas on Tuesday) will help make for some big cloud build-up

Inland areas are most exposed but coastal thunderstorms may easily form."

These thunderstorms could end up a breeding ground for even more extreme weather. Weather Watch says there is some risk of hail and even tornadoes over the coming days.

"The risk for hail or a small tornado would be underneath any of the biggest thunderstorm cells that form - most likely being categorised as a 'severe' thunderstorm," it said.

While the North Island is battered, however, large swathes of the South Island will escape relatively unscathed. The West Coast will be the country's sunniest place on Monday, with temperatures there also to be above normal.