MetService has upgraded a heavy rain watch to an orange warning for parts of the central North Island.

A front is moving onto the North Island from the west, bringing a period of rain to many parts of the island. Meanwhile, a slow-moving front is set to bring rain to the Westland District.

The heavy rain warning is in place for Bay of Plenty about and east of Whakatāne, including the eastern ranges, from 3pm to 5am Monday, Waikato south of Te Awamutu, inland Bay of Plenty west of Whakatāne, Waitomo, Taumarunui, Taupō, and Tongariro National Park from noon to midnight.

Streams and rivers may rise rapidly, surface flooding and slips are also possible and driving conditions may be hazardous, MetService warns.

The heavy rain watch is still in place for Westland District south of Franz Josef and North Taranaki including the Mountain/Taranaki Maunga until 9pm Sunday.

Thunderstorms may also hit in those regions, with rainfall amounts possibly reaching warning criteria in localised places, MetService said.

The heavy rain watch for Fiordland has been lifted as conditions eased there on Sunday morning.