Torrential rain has hit the Gisborne region and forecasters warn it will continue to affect the east coast over the next couple of days.
MetService reports some stations around Tairāwhiti/Gisborne have recorded just over 100mm since Friday afternoon, while Tauranga Airport has had 80mm.
The Gisborne District Council says its wastewater system has been flooded with rainwater, putting pump stations under pressure.
To relieve this pressure and prevent sewage from overflowing back into homes and onto roads, the emergency wastewater valve was opened into the Tūranganui River on Saturday night.
"The discharge is highly diluted with rainwater, but there's still a risk to health. Temporary warning signs are installed along the river and beach affected. We advise no fishing, gathering shellfish or water activities in rivers and beaches until at least five days after the valve is closed and warning signs are removed," the council posted to Facebook.
It added this is only done "when there's no other option" and the Hauora Tairāwhiti Medical Officer of Health has been notified.
Heavy rain watches continue for some eastern regions, with one in place for Gisborne/Tairāwhiti until 6pm on Monday, June 19.
"Rainfall amounts may approach warning criteria, especially about the ranges," MetService said on its website.
"Thunderstorms are possible. Note: The Wairoa District northeast of Nuhaka is now included in this watch."
Another covers the Bay of Plenty from Edgecumbe westwards until 6am on Monday, and a third is in place for Hawke's Bay south of Te Pohue until 9pm Monday.
For the South Island, a heavy rain warning covers eastern Marlborough south of Ward, with MetService advising there could be periods of heavy rain and amounts may approach warning criteria.
Meanwhile more rain is forecast later next working week as a low-pressure system moves onto northern New Zealand from the Tasman Sea on Thursday or Friday.
"There is low confidence rainfall amounts will reach warning criteria about Northland on Wednesday and Thursday, Great Barrier Island, Auckland north of Whangaparaoa, Coromandel Peninsula, Bay of Plenty west of Whakatane, and Tairawhiti/Gisborne on Thursday and Friday, and Hawke's Bay on Friday," MetService said.
