Coromandel Peninsula, Bay of Plenty and the Hunua Ranges are next “in the firing line” of severe rainfall, and western parts of the South Island are under a thunderstorm watch.

While “the worst is over” for Auckland and Northland, a front currently moving eastwards across the Bay of Plenty is expected to reverse direction on Thursday and move back towards the Coromandel Peninsula according to MetService.

An orange heavy rainfall watch is now in place for the Hunua Ranges and Coromandel Peninsula,with a total rainfall accumulation of around 30-50ml expected in the 18 hour-period from noon Thursday.

MetService forecaster Dan Corrigan said the amount of rain wouldn’t normally be enough to justify a watch, but the impact could be greater due to the recent flooding.

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“Given how saturated the ground is with all the rain that’s been had there in the last few weeks, it’s warranted to issue to a heavy rain watch for the area,” Corrigan said.

“Any significant rain could bring further impacts.”

MetService said the Coromandel had already received between 50 to 60mm of rain on Tuesday night, with peak rainfall rates reaching 16mm per hour.

The red heavy rain warning for Bay of Plenty west of Kawerau was lifted by MetService shortly after 8pm Wednesday, but an orange warning remained in place for a 24-hour heavy rainfall period from 8am Thursday.

It may cause surface flooding, slips and rivers to rapidly rise in the area, MetService warned.

Northern Gisborne and Westland are under an orange warning with Bay of Plenty expecting a further 50 to 80 mm of rain in a 14-hour period from 8pm Wednesday on top of what has already fallen.

Overnight, heavy downpours are also expected for Western Tasman, leaving heavy rain watches in place. They are forecasted to ease at 6.00am.

Northern Fiordland may also approach warning criteria levels of rain in the 26-hour period from 9.00am Thursday.

The heavy rain watch was lifted for Mount Taranaki with showers still possible, but the heaviest rains have passed, MetService said.

“Pretty much the entire North Island will be affected,” MetService meteorologist Karl Loots said.

Torrential showers soaked Auckland early on Wednesday, with downpours of 30 to 40mm per hour hitting the city in the morning.

Meanwhile, parts of Northland received 60mm of rain, with rainfall rates hitting 25 to 30mm per hour overnight Tuesday.

In the south, periods of heavy rain in Westland south of Otira, on the West Coast, are expected from the early hours of Thursday morning, and isolated thunderstorms are expected in the southern parts of the Canterbury High Country southwards through inland North Otago.

While the majority of the country is under a wet weather watch, Cantabrians are being warned to keep hydrated ahead of a four-day consecutive heatwave with temperatures set to reach 30C or above from Thursday.