MetService is warning of heavy rain, possibly heavy snow and northwest gales for parts of central and southern New Zealand

In Westland overnight tonight, especially south of Aoraki/Mount Cook, there'll be up to 180mm of rain at rates up to 20mm an hour.

Only slightly less rain is forecast at the same time for Fiordland around and north of Doubtful Sound.

From midnight in the headwaters of the Canterbury lakes and rivers south of Arthur's Pass, and in the headwaters of the Otago lakes and rivers, some 130mm of rain is forecast, falling as snow along the ranges.

From 11 in the morning, Wellington is in for severe gale-force northerly winds, up to 120km/hr in exposed places.

There's an orange heavy rain warning for Mount Taranaki from around 10 in the morning.