Twenty-four hours of heavy rain is looming for the top half of the North Island and forecasters are particularly concerned for the Bay of Plenty.

Orange heavy rain warnings lasting around 24 hours are in place for the Coromandel Peninsula from 2pm, Bay of Plenty from 8pm, Tongariro National Park from 10pm and Gisborne/Tairāwhiti, north of Ruatoria from midnight.

Severe thunderstorm watches were also in place for the Bay of Plenty and Rotorua until 3pm today.

“Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible,” MetService warned.

🌧️ Severe Thunderstorm Watch issued for Bay of Plenty 🌧️

Narrow bands of heavy rain are moving westward across the Bay of Plenty today. There is a risk of downpours with or without lightning.

This watch is before the wider orange heavy rain warning that begins later today. pic.twitter.com/P0SRKSkytd

— MetService NZ (@MetService) November 17, 2025

Earth Sciences New Zealand (formerly Niwa) forecaster Chester Lampkin told the Herald this morning that an area of low pressure in the Tasman Sea and a cold front coming in from the southwest would bring a big plume of moisture from the Tasman.

As well as heavy rain for many, warm nights could also be expected.

“We call it an atmospheric river because of the amount of moisture coming with it,” Lampkin said.

“There is an area of high pressure to the east that is blocking the weather pattern, where it slows the weather down to almost a standstill, which makes the storms move a little bit slower.”

MetService forecaster Alec Holden told the Herald a lot of rain was spread across the North Island.

Up to 120mm of rain was expected in Gisborne/Tairāwhiti, 180mm in Coromandel Peninsula and up to 200mm in Bay of Plenty, with localised downpours of 25 to 40mm/h possible, the largest accumulations likely west of Whakatāne.

Forecasters were most concerned about the Bay of Plenty, Holden said.

“There is a moderate chance Bay of Plenty gets upgraded to a red warning in terms of rainfall.”

The agency encouraged people to clear their drains and gutters, avoid low-lying areas and drive cautiously.

Wastewater overflow

Daily water sampling of Rotorua’s Waikuta Stream and the nearby lake area is ongoing following last week’s wastewater overflow.

Rotorua Lakes Council was alerted by contractors around midday on November 11 of damage to a large wastewater pressure pipe that occurred while work was being carried out in the area.

The overflow was stopped, with seven sucker trucks removing wastewater, and the damage to the rising main was repaired.

Rotorua Lakes Council said today the latest available results showed that E. coli levels were improving, but were not within recommended contact levels.

“With more rain forecast, we anticipate there could be increases in results for a number of streams over the next few days.

“As a precaution, it is advised there should be no contact with the water between Beaumont Rd and the Waiowhiro Stream for at least 48 hours after the anticipated heavy rainfall this week.”

Warning signage has been installed at various points along the foreshore and lake access points.