Weather: Heavy rain warnings for South Island, severe gales to batter lower North Island

Heavy rain is expected to hit southern regions over the weekend.

MetService said western areas of the South Island were likely to get heavy rain on Saturday.

Severe gales would follow on Sunday, while snow would fall in Otago and high-altitude roads across the South Island.

"A series of fronts, embedded within a strong and moist northwest flow, move over New Zealand today and tomorrow, followed by a change to strong, colder southwesterlies," the forecaster said on Saturday morning, urging people to keep up to date.

A heavy rain watch was issued for Westland and areas south of Aoraki/Mt Cook, lasting from 9am Saturday to 9am Sunday. Thunderstorms were possible, with a moderate chance of upgrading to a warning.

Orange strong wind warnings were also in place for Tararua District, Wairarapa, Wellington and Marlborough Sounds for Sunday morning.

A heavy snow watch will be in place for Southern Lakes and Central Otago from 5am to 4pm Sunday, above 700m, with a moderate chance of upgrading to a warning.

And MetService said strong wind was possible for inland Hawke's Bay about and south of State Highway 5 between 8am and 2pm Sunday; and in Marlborough about and east of the Kaikoura ranges between 7am and 3pm Sunday.

Both areas could experience severe gales in exposed places.