MetService has issued a Severe Weather Watch notice with westerly gales forecast for parts of southern and central New Zealand, and heavy rain for Northland.

"Strong to gale westerlies bring showery conditions to southern and central New Zealand this weekend," says a MetService spokesperson.

"A Strong Wind Watch is in place for Wellington this morning.

"On Sunday, west to southwest winds strengthen about the South Island. A Strong Wind Warning is in force for coastal Southland, Stewart Island and Clutha."

MetService say that a Strong Wind Watch also covers the Canterbury High Country, and remaining parts of Otago and Southland not covered by the Strong Wind Warning.

On Monday, a low pressure system is forecast to move onto the upper North Island, bringing a period of heavy rain and strong to gale easterlies. A Heavy Rain Watch is now in place for Northland.

People are advised to keep up to date with the latest forecasts in case any changes are made or more areas are added.

A Heavy Rain Watch has been issued for the north and east of Northland. This is valid for 12 hours from 9am to 9pm on Monday. A period of heavy rain is forecast and rainfall accumulations may approach warning amounts.

A Strong Wind Watch has been issued for the following regions:

Area: Wellington
Valid: 2 hours from 9:00 am to 11:00 am Saturday
Forecast: Northwest winds may approach severe gale in exposed places.

Area: Canterbury High Country, Queenstown Lakes, Central Otago,
Dunedin, and inland parts of Clutha and Southland
Valid: 11 hours from 6:00 am to 5:00 pm Sunday
Forecast: Westerly winds may approach severe gale in exposed places.