A New Zealand MetService severe weather warning is in place for the Bay of Plenty with heavy rain approaching.

The warning includes the Coromandel Peninsula, Bay Of Plenty and Taupo.

It is for an active front over the Tasman Sea expected to move slowly eastwards across New Zealand during Wednesday and Thursday.

This front is preceded by a strong and very humid northeasterly flow.

Rain is likely for much of the country, with the heaviest falls in the west and north of both islands.

As the front approaches the North Island from Wednesday afternoon through to Thursday morning warning amounts of rain are expected for Mount Taranaki, Northland, the north of Auckland, Coromandel Peninsula, Bay of Plenty and Tongariro National Park.

Rain in most of these areas should ease from the west on Thursday, however, heavy rain is expected to persist in the east of the Bay of Plenty overnight Thursday.

In the 18 hours from midnight Wednesday in the Coromandel, the MetService is forecasting 70-100mm of rain, with peak intensities of 15-20mm/hour on Thursday morning.

In the 30 hours from midnight Wednesday to 6am Friday in the Bay of Plenty, the MetService is forecasting 100-150mm of rain could accumulate.

It forecasts peak intensities of 15-20mm/hour in the west on Thursday morning and over the entire area Thursday afternoon.

It expects rain to ease in the west on Thursday evening and in the east early Friday morning.