Weather: Heavy rain and gale alerts for South Island while North Island stays warm

Heavy rain and wind watches are in place across the South Island, but warm weather should be sticking about for much of the North Island.

Up to 230mm of rain could fall in Westland and the Canterbury headwaters south of Arthurs Pass as MetService has placed a heavy rain warning on these two areas.

Thunderstorms are likely in Westland, while both areas might be impacted by streams and rivers rising rapidly, surface flooding, slips and difficult driving conditions.

A strong wind warning has been issued for the Canterbury High Country and the Canterbury Plains near the foothills, with severe gale northwesterlies possibly hitting 120km/h in exposed places.

Fiordland is under a strong wind watch from 2am to 8am, but MetService said this has a moderate chance of being upgraded to a warning.

Elsewhere, heavy rain watches have been issued for Tasman, Buller, the Grey District, the Otago headwaters and Fiordland north of Doubtful Sound, with periods of heavy rain expected for all these locations.

Severe weather watches and warnings are in place across the South Island while the North Island remains fine for most of the day. Photo / MetService

From noon to midnight, parts of the south coast of the North Island have low to moderate risks of thunderstorms and Wellington can expect 10-25mm/h of rain.

However, the upper North Island should be in for a warm day with little rain.

Auckland, Hamilton and Whangārei are predicted to get highs of 26C, but there is the possibility of some cloud and isolated showers.

The sunny weather might not last for long in the North Island as MetService expects rain to spread north and east in the morning and afternoon on Friday, with some of this possibly being heavy.

Showers continue in the South Island on Friday in the west and south, but should ease later in the day.

Looking to the weekend, the North Island is predicted to experience scattered showers that will gradually clear from the south on Saturday, while the south and west of the South Island continue to see showers.