MetService warned the area could expect up to 140mm of rain about the ranges, and up to 90mm on the coast.
It also said thunderstorms are possible with peak rainfall intensities expected to reach 25mm/h.
Gisborne’s State Highway 35, badly impacted by extreme weather events earlier this year, has flooded on the Mangatuna side of a new bridge.
Flooding has also made driving dangerous on SH35 between the Rototahi and Waihau turnoffs, Uawa Civil Defence said.
“Periods of heavy rain return early Friday and spread throughout the Tarawhiti/Gisborne region as winds turn more easterly. Heavy rain is expected to continue through the weekend, with further warnings likely to be issued.”
Northland is first in the firing line. A watch is in place from 9am today until 4am tomorrow.
One forecaster has warned of up to 50mm of rainfall “in just a few hours” there.
Thunderstorms possible in Auckland overnight
North Auckland, including Great Barrier Island, will be under a rain watch for 12 hours from 9pm today.
MetService said northeasterly winds could get up to 80km/h about Auckland and the temperature should reach 17C.
Partly cloudy conditions with isolated showers are forecast for the city throughout today. Heavy rain may spread south from late afternoon with a risk of thunderstorms, MetService said.
Some Gulf Harbour ferries will be affected and replaced by bus services and taxis, said Auckland Transport.
The downpours are set to linger into the weekend with highs likely to remain about 16C to 17C.
Heavy rain watch for Coromandel, Bay of Plenty, Marlborough
A 35-hour watch is in place for the Coromandel Peninsula and Bay of Plenty from 1am Thursday to midday Friday as the low-pressure system responsible for the weather moves down.
Heavy rain watches have also been issued for the Ruahine Range, Kaweka Forest Park and eastern Marlborough, south of Ward.
MetService meteorologist Alwyn Bakker said the prolonged rainfall in the Bay of Plenty, Coromandel and Gisborne could see flooding and slips even if warning criteria weren’t reached.
Parts of Tairāwhiti/Gisborne recorded over 60mm of rain in the 24 hours from 10am on Sunday, and Gisborne itself saw about 30mm in that period.
Further south, a few locations in Hawke’s Bay and the Wairarapa also saw about 30mm.
The National Institute of Water and Atmospheric Research said its high-resolution forecasting models showed 50mm of rain was possible “in just a few hours” in Northland throughout today.
Further south, Wellington is set for a fine day with clouds in the evening. MetService said the city would get light winds and then stronger easterlies in the afternoon.
The capital has a forecast high of 15C while Christchurch has a forecast high of 13C.
The Garden City is in for a mostly cloudy day with some fine spells in the afternoon, turning to patchy drizzle in the late evening. Dunedin is also set for a 13C high with a fine day.
Raphael Franks is an Auckland-based reporter who covers breaking news. He joined the Herald as a Te Rito cadet in 2022.
