More bad weather is forecast for Canterbury, with severe heavy rainfall warnings in place.

Heavy rain is also forecast for parts of Marlborough, eastern Otago and Southland, with severe gales for parts of the South Island.

Metservice has updated its forecast and said a complex low pressure system over central and northern New Zealand is expected to continue bringing widespread heavy rainfall into the Canterbury region, which remains under a Red Warning.

Heavy rain is also forecast for Marlborough about and south of Kaikoura where an Orange Warning remains in force.

A period of heavy rain is also possible about eastern parts of Otago and Southland where Heavy Rain Watches are now in place.

This low pressure system is forecast to move away to the east of the country on Monday.

Severe gale southeasterlies are expected along the South Island west coast south of Hokitika, and also for the Canterbury coast north of Ashburton, including Banks Peninsula.

The remainder of Canterbury remains under a Strong Wind Watch, while southern parts of Marlborough are also now covered by a Strong Wind Watch.

Metservice said dangerous river conditions and widespread flooding are expected.

Slips and floodwaters are likely to disrupt travel, making some roads impassable and possibly isolating communities. Power outages are also likely.