An incoming subtropical storm that is set to hit New Zealand tomorrow is extending its reach to the Coromandel and western Bay of Plenty, MetService has confirmed.

The active front associated with a subtropical low is currently south over the upper North Island, set to hit on Sunday and Monday.

Auckland Emergency Management told Aucklanders yesterday to “keep an eye on forecasts” and prepare for bad weather, now MetService has included two other regions in the exposure area.

Coromandel Peninsula can expect between 150 and 200mm of rain from early Sunday morning to late Monday, the Government weather forecaster placing it under an orange-level warning.

The active front associated with a subtropical low is currently south over the upper North Island, set to hit on Sunday and Monday. Photo / MetService

Peak rates of rainfall will be on Sunday evening for the coastal region.

As for the Bay of Plenty, regions west of Kawerau - including Rotorua - should expect heavy downpours from Sunday evening through to Tuesday morning.

The regions are now under heavy rain watch along with Northland and Auckland, which will experience a similar level of rain.

In a social media tweet, MetService did clarify there was still uncertainty around where exactly the worst of the rainfall would hit, urging residents to keep their eyes on weather forecasts over the coming days.

Auckland Emergency Management’s general manager, Paul Amaral, said in a statement to the media that those living in an area prone to flooding or isolation should plan to secure their property.

“We’re expecting high winds and rain for some areas of Auckland, so remember, in a storm, consider your travel plans carefully, never drive through floodwaters and phone 111 if your life is in danger,” he said.

The regions are now under heavy rain watch along with Northland and Auckland, which will experience a similar level of rain. Photo / MetService

“We are expecting areas on Auckland’s east coast, including Whangaparāoa and Aotea Great Barrier, to be hit with the most intense rainfall and wind.

“Charge your phones, ensure you have a torch ready and check your emergency plan.”

Auckland is forecast to get eight days of wet weather from today, with heavy downpours and gales forecast for the first few days.

MetService forecaster Jessie Owen said the sub-tropical low-pressure system packed with strong winds and rain was bearing down on New Zealand, dragging a lot of warm, wet air with it.

Owen said next week the low would keep tracking south, dragging the rain across most of the country, unleashing the worst weather on northern and western regions.

“After that, [the] low moves to the south [and] we’re into a general wet disturbed northerly flow,” he said.

“We’re looking at several bands of rain coming in from the north. It’s all looking a bit messy and not particularly well-defined, but wet.”

Yesterday, Auckland Mayor Wayne Brown requested a top-level briefing from key emergency management staff ahead of the tropically-fuelled storm.

“The mayor has requested a briefing from emergency management staff. At this stage, we have no further information,” said a spokesperson.