People in the Bay of Plenty and Coromandel Peninsula are being urged to prepare for heavy rain this weekend.

The MetService is forecasting heavy rain and northwest gales for parts of New Zealand and has issued a severe weather watch for both regions.

"A series of fronts move across the country from the Tasman Sea today, bringing heavy northwesterly rain to some western areas, and gales to central regions," says the weather organisation in its latest update.

"Over the weekend, a low pressure system is forecast to approach and then cross northern New Zealand from the northwest. An associated front is expected to bring a burst of heavy rain to northern regions.

"People are advised to keep up to date with forecasts as changes could be made."

Heavy Rain Watch
Area: Coromandel Peninsula
Valid: 12 hours from 11pm Sat 18 Nov to 11am Sun 19 Nov
Forecast: A period of heavy rain. Rainfall amounts may approach warning criteria, especially about the ranges.

Area: Bay of Plenty west of Whakatane
Valid: 15 hours from 2am Sun 19 Nov to 5pm Sun 19 Nov
Forecast: Periods of heavy rain. Rainfall amounts may approach warning criteria, especially about higher ground.

Strong Wind Watch
Area: Wairarapa, Wellington, and Marlborough north of Blenheim
Valid: 9 hours from 10am Fri 17 Nov to 7pm Fri 17 Nov
Forecast: Northwest winds may approach severe gale in exposed places.