Metservice has issued a severe weather watch for parts of the North Island and Fiordland.

'Heavy rain is possible for Auckland, Great Barrier Island, the north of Coromandel Peninsula, and Fiordland,” says a MetService spokesperson.

'A trough is forecast to bring rain or showers to Auckland, Great Barrier Island and Coromandel Peninsula about and north of Whitianga Saturday morning.

'The rain or showers may be heavy, with thunderstorms and localised downpours also possible.”

Meanwhile, a front approaching Fiordland becomes slow-moving just to the west of the South Island on Saturday morning. This front is forecast to bring rain to Fiordland, which may be heavy for a time.

People are advised to stay up to date with forecasts in case any changes are made or new areas are added.

A heavy rain watch has also been issued for these Auckland, Great Barrier Island, and Coromandel Peninsula about and north of Whitianga, with thunderstorms and localised downpours also possible. This watch is valid until 10am on Saturday, and rainfall accumulations may approach warning criteria in localised areas.