Already-sodden areas of the North Island continue to be on alert as heavy downpours threaten to bring more flooding and slips.

Along the North Island’s East Coast in Tolaga Bay, flooding has already impacted several roads. Tairāwhiti Civil Defence said streams and rivers could rise rapidly, and slips and flooding were possible.

Flooding shut down SH35 between Okitu and Ruatoria in Tairāwhiti at 4pm yesterday. Gisborne’s State Highway 35, badly impacted by extreme weather events earlier this year, flooded yesterday on the Mangatuna side of a new bridge.

MetService issued an orange heavy rain warning for Gisborne about and north of Tolaga Bay at noon yesterday, which will last until 3pm today.

The forecasting agency warned 100mm to 140mm of rain in the ranges, and 60mm to 90mm of rain about the coast was to be expected, with thunderstorms possible.

By 4pm yesterday, 55mm of rain had been recorded in the Raukmara Range in northern Tairwhiti, most of it since noon, according to MetService.

Despite the possibility of a brief reprieve in that region during the course of tonight, MetService predicted that bouts of heavy rain would resume early Friday and would spread throughout Tairwhiti as the winds shifted more easterly. Through the weekend, there was forecast to be heavy rain in the area.

MetService meteorologist Alwyn Bakker said the prolonged rainfall in Bay of Plenty, Coromandel and Gisborne caused by the low-pressure system from the Tasman Sea may cause flooding and slips even if warning criteria were not reached.

A low-pressure system just to the west of Northland on Wednesday afternoon is responsible for the rain, which is predicted to gradually move across the northern part of the country through Saturday.

A heavy rain warning is in place for Northland which began at 8pm yesterday evening and is expected to last until 5am this morning.

Between 9am and 5pm yesterday, Kaitaia received about 50mm of rain, with about 20mm falling within the hour from 11am to noon.

MetService warned a further 50 to 70 mm of rain was expected to fall last night, with peak rates of 15 to 25 mm/h, particularly in the north and west. Thunderstorms are also possible.

North Auckland, including Great Barrier Island, was placed under a heavy rain warning by MetService at 9pm last night, which is expected to last until 9am this morning.

Throughout today, Auckland is forecast to see periods of rain or showers, with some heavy and thundery falls. The downpours are set to linger into the weekend.

As the low-pressure system that’s causing the weather moves south, a 35-hour watch is in effect for the Coromandel Peninsula and Bay of Plenty, which began at 1am this morning and is expected to last until 12 pm on Friday.

140 to 180 mm of rain is expected, especially about Coromandel Peninsula, with peak rates of 15 to 25 mm/h.

Weather forecasting agency Niwa reported the storms impacting these areas would be strong, producing heavy rain and possibly an isolated tornado.

Niwa also reported that 60,000 lightning strikes were recorded near the top of the country in the Tasman Sea.