The West Coast of the South Island is likely to bear the brunt of a significant band of bad weather moving towards New Zealand from the Tasman Sea.
Earlier predictions had warned of rain and strong winds for most of the country, however updated reports have heavy rain and thunderstorms confined to the west of the South Island.
"We're talking about half a metre, or thereabouts, of rain falling over a 1-2 day period, so that is a significant amount even for that part of New Zealand and since it has been fairly dry in those areas, that certainly is quite a change," MetService forecaster Peter Little told Newshub.
Central and northern parts of New Zealand will remain largely unaffected by rain, according to WeatherWatch.
"For those needing rain in the North Island, this front will weaken significantly as it moves northwards around late Wednesday and Thursday, but there may be some isolated downpours which bring relief."
However gale warnings were issued to the Cook Strait and Castlepoint by MetService on Monday morning.
MetService is asking those in the south of the South Island to monitor weather forecasts vigilantly.
"Keep up to date with the severe weather warnings and watches because certainly it's going to be fairly rough in some parts of the country, particularly the West Coast of the South Island this coming week," Little said.