Strong winds that caused some damage in Dunedin are moving north ahead of a front that'll dump heavy rain, mostly in the west.
The culprit is a low pressure system from Sydney that's deepening in the Tasman Sea, says Weatherwatch.co.nz.
As it moves closer to the South Island the winds between it and a large high north of the country are increasing.
Gusts of more than 100km/h knocked trees and some powerlines down in Dunedin on Sunday morning but are not predicted to worsen.
Wellington and many North Island regions are also predicted to get a battering.
By midnight the centre of the low will be over the top of Central Otago.
Rain has been falling in western areas of the South Island and it's also heading north. Some rain may make it to drier eastern areas but it's "hit and miss", Weatherwatch.co.nz says.
The MetService tweeted gusts of 104lkm/h were recorded in Dunedin Hills and gale force winds are moving up New Zealand.
In a severe weather warning, MetService says the front may dump up to 180mm of rain on the ranges south of Otira in the 19 hours from 10am on Sunday.
Rain at the rate of 20mm per hour, with thunderstorms, is possible on Sunday afternoon.
About 100mm of rain may also fall within 10km east of the main divide of the Southern Alps during the same period, affecting the headwaters of Canterbury lakes and rivers south of Arthur's Pass.
This is enough to cause surface flooding and slips.