Weather: Thunderstorms to hit the North Island

Rain, thunderstorms and squally winds will hit the North Island today, due to an active front moving across the country.

MetService is warning of thunderstorms as the front crosses. The risk is moderate for Northland, Auckland, the Coromandel, the Waikato, eastern Taumarunui, Taupo, Rotorua and the western Bay of Plenty.

"Any thunderstorms that develop here are expected to produce localised heavy rain of 10 to 25mm per hour, strong wind gusts around 90 km/h and there is a risk of small tornados," MetService said.

Due to the poor forecast, the NZ Transport Agency (NZTA) has revised the expected opening of the Waiho Bridge until the weekend.

The bridge was destroyed in devastating storms last month, cutting off the Franz Josef township.

"Teams have worked hard to keep this project on track but last night's and today's rain and rapidly rising river levels have pushed this project beyond Friday," said Moira Whinham, NZTA's West Coast maintenance contract manager, on Wednesday.

There is also a risk of heavy rain with thundery downpours later today for Wellington, southern Wairarapa, the Marlborough Sounds and the northern Marlborough coast.

It's not all bad news, though. MetService predicts that, by the end of Friday, a ridge will have spread over much of the country, bringing settled weather to most places.

That settled weather is forecast to continue into the weekend.