UPDATED: The MetService has issued a severe weather watch for the Bay of Plenty as a heavy rain band moves down from the Coromandel.

A complex trough lies across the upper North Island, and should slowly weaken and move away to the southeast tomorrow, says a statement from the MetService.

A rain band is currently moving over the Bay of Plenty. Image: MetService.

"Rain is likely over most of the northern half of the North Island, with the heaviest falls expected to be in the northeast, from the Coromandel Peninsula to northern Hawke's Bay.

"This Watch is for the possibility of heavy rain reaching warning criteria in the Coromandel Peninsula and Bay of Plenty."

In the Coromandel, the MetService is expecting rain to continue today and tomorrow, with heavy falls at times.

In the Bay of Plenty, periods of heavy rain are likely today and tomorrow, with the heaviest falls expected to be west of Te Puke and also near the coast.

Latest update on areas at risk of heavy rain. ^Lisa https://t.co/PJDsdVdu5h

— MetService (@MetService) September 20, 2016

Earlier:

A severe weather watch for heavy rain is in place for the Coromandel Peninsula as a front moves across northern New Zealand.

The Metservice is forecasting heavy rain for both the Coromandel and Bay of Plenty, but no watch has been issued for the Bay as of yet.

According to the weather organisation, a front was expected to move across northern New Zealand overnight and today, bringing bursts of heavy rain with it.

'The front may stall for a time over northern Auckland or the Coromandel Peninsula on Wednesday morning, with the potential for a sustained period of heavy rain.”

In the Bay of Plenty, the MetService is forecasting rain, possible heavy for a time, with southeasterlies.

There is only supposed to be the occasional rain tomorrow, with southeasterlies dying out.

Friday and Saturday are expected to be fine, with the chance of the odd shower.

North Auckland clocked up 40mm of rain overnight, with 25mm elsewhere in Auckland. More to come, but patchy, see https://t.co/7k3nmdWQwx ^GG pic.twitter.com/piKfKBuSNM

— MetService (@MetService) September 20, 2016