A heavy rain watch has been issued for parts of the North Island, including the Coromandel area.

The MetService is forecasting heavy rain for parts of the North Island and upper South Island.

"A slow-moving front just west of the North Island should begin to move eastwards on Wednesday. This front brings periods of northerly rain to much of the North Island and upper South Island.

"The heaviest rain is expected in the north and west, with thunderstorms and localised downpours of 25 to 40mm and possibly more.

"People are advised to keep up to date with forecasts, as further areas may be added to the Watch and Warning."

HEAVY RAIN WATCH

Area: The west of Northland
Valid: 15 hours from 2pm Tuesday to 5am Wednesday
Forecast: Periods of heavy rain, with thunderstorms and localised downpours possible. Rainfall amounts may approach warning criteria.

Area: Auckland and Coromandel Peninsula
Valid: 8 hours from 3am to 11am Wednesday
Forecast: A period of heavy rain, with thunderstorms and localised downpours possible. Rainfall accumulations may approach warning amounts.

Area: Waitomo, Taumarunui, Taupo, Taihape, inland Whanganui and South
Taranaki
Valid: 14 hours from 11am Tuesday to 1am Wednesday
Forecast: Periods of heavy rain, with thunderstorms and localised downpours possible. Rainfall amounts may approach warning criteria.

Area: Horowhenua Kapiti Coast
Valid: 9 hours from 6pm Tuesday to 3am Wednesday
Forecast: A period of heavy rain is expected this evening and overnight tonight. Rainfall accumulations may approach warning amounts.

Area: The Marlborough Sounds
Valid: 15 hours from 3am to 6pm Wednesday
Forecast: A period of heavy rain. Rainfall accumulations may approach warning amounts.

Area: Wellington
Valid: 36 hours from 6pm Tuesday to 6am Thursday
Forecast: A period of heavy northerly rain expected this evening and overnight tonight. A period of heavy southerly rain is then expected later Wednesday and early Thursday. Both rain events may approach warning accumulations.