A main highway in the Coromandel has been closed until further notice, due to instability caused by heavy rain.

State Highway 25A, along with the Tapu-Coroglen and 309 are the roads now closed, according to a police spokesperson.

"A detour route is in place - State Highway 25 around the edge of the peninsula and State Highway 2 via Karangahake Gorge," says the police spokesperson.

"Motorists should expect longer travel times using the detour route."

This comes as a subtropical low is lashing the North Island today with wet weather.

"The low's associated fronts bring rain or showers to the North Island. The heaviest falls are likely in Coromandel Peninsula and Bay of Plenty and there is moderate confidence that a heavy rain warning will be required on Sunday," says a MetService spokesperson.

Sunday's downpour will not be the end of the rain, according to MetService.

"Another sub-tropical low approaches the northwest of the North Island on Monday, then moves southwards past the west of New Zealand during Tuesday and Wednesday with it's associated fronts affecting the country.

"There is moderate confidence of rainfall accumulations reaching warning criteria in Northland on Monday and Tuesday, while for Auckland and Coromandel Peninsula, confidence is low on Monday then increases to moderate on Tuesday. There is also low confidence of heavy rain for western Bay of Plenty on Tuesday.

"In addition, there is low confidence of northeast winds reaching severe gale at times in Northland and Auckland on Monday and Tuesday.

"During Tuesday and Wednesday, the South Island is affected and there is low confidence of warning amounts of rain for northwest Tasman Sea during this time and also for central and southern Westland and northern Fiordland on Wednesday."