A heavy rain watch is in place for the Bay of Plenty as a slow-moving weather system approaches the upper North Island.

The watch covers Bay of Plenty areas west of Edgecumbe, including Tauranga and Western Bay communities, from 4am Tuesday until 6am Wednesday.

In its latest weather update, MetService said periods of heavy rain were expected during the 26-hour period, with localised downpours possible.

Rainfall intensities could reach 25mm to 40mm per hour in some areas.

Forecasters warn that rainfall totals may exceed heavy rain warning criteria in localised spots, particularly where downpours develop.

The Bay of Plenty watch forms part of a wider weather system affecting much of the northern North Island.

Heavy rain watches have also been issued for Northland, Auckland, Great Barrier Island, the Coromandel Peninsula, Waikato and parts of the central North Island.

MetService said slow-moving rain bands were expected to affect large parts of New Zealand from late Monday through to early Wednesday, with the potential for thunderstorms and intense localised rainfall in northern regions.

There is currently a moderate chance the Bay of Plenty watch could be upgraded to a heavy rain warning.