A red heavy rain warning has been issued as a “significant” weather event bears down on the upper North Island.

A deep sub-tropical low approaching New Zealand will bring heavy rain and strong northeast winds for Northland, Auckland, Coromandel and Bay of Plenty from late today through tomorrow and Friday.

“This will be an impactful multi-hazard event,” MetService warned.

A red heavy rain warning has been issued for Northland, east of Kaikohe from Doubtless Bay to Whangarei, from 4pm today to 4am Friday, with MetService warning that dangerous river conditions, significant flooding and slips could bring a threat to life.

MetService said to expect 270mm to 320mm of rain with peak falls of 25mm/h to 40 mm/h and possibly greater from Thursday afternoon through to early Friday morning.

The remainder of Northland, Auckland and Great Barrier Island have had orange warnings for wind and rain issued.

Meteorologist Silvia Martino told the Herald rain would start spreading south into Northland this afternoon.

“The rain starts to get heavy in the evening and it really is a long period of heavy rain for them,” she said, warning of consistent rain “for a couple of days”.

MetService said the heaviest rain was likely in the upper North Island, especially from Northland to western Bay of Plenty.

“Downpours, flooding, and slips are possible on Thursday and Friday.”

Between 130 and 200mm of rain is forecast to fall across Northland, Martino said.

“In the northern and eastern parts that are most exposed, up to 250mm is possible.”

Heavy rain warnings are also forecast to come into force for Great Barrier Island and the Coromandel Peninsula from early tomorrow morning until Friday night.

Martino said the rain would begin to move across Auckland today; however, the heaviest rain would drench the city tomorrow and into Friday.

A heavy rain watch has been issued for Auckland from 3am tomorrow until 12pm Friday.

There is a high chance the watch would be upgraded to a warning, MetService said.

The wet weather will continue to spread southward tomorrow, with the Coromandel and Bay of Plenty set to be drenched in the morning, Martino said.

Heavy rain and strong winds will also affect parts of the South Island, especially for Tasman and the West Coast.

The powerful winds were forecast to bring heavy swells to coastal areas.

“Expect heavy swells with heights exceeding 4m to affect coastal areas of the North Island from Wednesday night,” MetService said.

“Later in the week, big waves will affect the South Island, with swell heights possibly exceeding 6m, especially in the western coastal areas.”